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} March 7, 1879.
Determination of Specific Gravities. THE CHEMICAL NEW s. üretimi come to the one through which it sinks, then I have
got the tenacity to within 2 grains. The intermediate
number will be found to support the weight for exactly the VOL. XXXIX. No, 1006.
right time. The number of grains required I call the
give the same stiffness as 18 lbs. of the other.
NOTE ON CHLORIDE OF CALCIUM. In some articles inserted in this journal the author stated
By O. GLUGE, Sarrebruk, that pure steel, nearly free from phosphorus and sulphur and containing 25 to 30 per cent of carbon, stands easily the process of welding, if, indeed, the work is done with The manufacture of soda by the ammonia process has, care and by clever workmen.
during the last few years, been much developed, owing to It may be mentioned here that to a steel ship-plate, 2 ft. the advances made by Mr. E. Solvay, and is likely to wide and g inch thick, a steel plate (2' X 2' x 3") was become more generally employed. It is possible that it easily welded, and a perfectly clean and good joint was may ultimately supersede Leblanc's method, as improvereceived.
ments are being constantly introduced into it. In another case steel strips (6" x 4" x 1") containing The reaction which occurs in this manufacture, as all 25 to 26 per cent of carbon were welded together ; very your readers are aware, takes place between bicarbonate often aíter cooling the plate was bent double, through of ammonia and chloride of sodium. Bicarbonate of soda the weld, without the least fracture in or near the is precipitated and hydrochlorate of ammonia remains in welded part.
In some experiments such plates were solution. The bicarbonate is separated by filtration, and bent at a dark heat, and they often, not always, resisted the solution is employed to furnish fresh bicarbonate of this severe test, as it is known that at this temperature ammonia. This is done by distilling the solution with the steel is more liable to break. These trials show that lime; then ammonia is disengaged and a strong ley of Russian Bessemer steel is of a very good quality.
chloride of calcium is left in the distilling apparatus.
I am anxious to direct the attention of your readers to this latter product, which is formed in considerable quan
tity and which is commonly thrown away as useless, as TENACITY OF STARCH,
it has hardly been employed hitherto in manufacturing
processes. By GEORGE WHEWELL, F.I.C., F.C.S.
It would be very desirable that men of science and
manufacturers should endeavour to ascertain if a more In consequence of the large quantity of farina (potato extended use could be made of a product which can be starch) which is used for the sizing and stiffening of yarn got at such a cheap rate. The manufactures of soda by and cloth, the question often arises-Given several samples the process above mentioned can furnish chloride of of starch, which will make the stiffest cloth and which calcium in quantity, in solution, in crystals, or even in the has the greatest tenacity? To my mind the best method fused state io diminish the cost of carriage. devised so far is the one used by Shier, and is as follows:24 grains of the sample of starch are mixed with 400 grains of distilled water, and hoiled with constant stirring for three minutes, then poured into conical test-glasses and allowed to stand for iwo hours; at the end of which time DETERMINATION OF SPECIFIC GRAVITIES. a flat metal disk seven-tenths of an inch in diameter, and
By S. F. PECKHAM. not weighing less than 50 grains, is placed on the jelly and weights added until the skin is broken and the disk sinks.
In the Chemical News (vol. xxxviii., p. 300) I notice an In working the above method I find a difficulty in mani-excellent article “On the Determination of Specific pulating the weights on account of the smallness of the Gravities." The author's points are well taken in referdisk. If after a 50. or 100-grain weight has been placedence to the importance of some uniform method either of on the disk you attempt to place a few smaller ones on performing the operation or of confuting results, and his also, the pressure is exerted unevenly, and the jelly is cut suggestions could with great propriety be referred to some by the edge of the disk and not broken uniformly. I committee of one of the Societies for a report and recomhave devised the following modification, which I have mendations that might be generally adopted. used for the last three years, and find it to answer very Having occasion some years ago to take the specific well. The principle is to ascertain the number of grains í gravity of some small quantities of distillates from petro. required of any sample of starch which, when made into leum products, I was led to adopt the following method, a jelly, will suppori a 100-grain weight for five minutes which was found to be entirely successful with so small a without breaking the skin. I have examined a large num- quantity as 3 cubic centimetres. ber of samples of farina, and find the number of grains I prepared a cube of aluminium, which was intended to required is from 18 to 28.
be of 1 c.c., but was accidentally obtained smaller. This To determine the tenacity of a sample of farina I take, was suspended by a platinum wire of the smallest size, say, six conical shaped test-glasses 1 ounce capacity, and and weighing only a few milligrms. The wire was first label the feet 18, 20, 22, 24, 26, and 28. Using a 2-ounce weighed, and then attached to the cube, which was then evaporating dish, I weigh out 18 grains of the farina, mix weighed in air, and then weighed just immersed in disit with 26 c.c. of distilled water, and boil with constant tilled water, and then in the oil. The difference between stirring for three minutes. Pour it into the test-glass the weight in the air and in water gave the weight of the marked 18, and shake to make the surface of the jelly water; the difference between the weight in air and in level, book the time, and allow to cool for exactly two oil gave the weight of the oil. The weight of the oil hours. At the end of this time I take a 100-grain weight divided by that of the water gave the specific gravity of (mine being thirteen-twentieths of an inch in diameter), the oil. and place it on the jelly. If it is supported for more than This method admits of perfect control of the volume of
New Substitute for Litmns.
March 7, 1879. the liquids compared, and of just as perfect control of the worked on this occasion ceased to indicate with sulphuric temperatures as any other method. Moreover, it admits acid when more dilute than 1 to 50,000. The new indi. of very rapid execution and of operating on very small cator, on the other hand, remained sensitive to i part of quantities of liquid. For taking the specific gravity of all sulphuric acid in 100,000 of water. ordinary oils and other non-corrosive liquids a cube of The solution of the indicator which I employ is made aluminium would be superior to a cube of platirum, on by dissolving 1 centigramme in 100 c.c. of distilled water, account of its lower specific gravity, and its permanence and contains therefore : part in 10 000. Even at this in the air renders it superior to any other of the so-called | great dilution the liquid is of a full orange colour. It is base metals.
worthy of remark that i centigramme of the substance is For the class of liquids named I have found the results sufficient for five hundred determinations of acid or alkali; obtained by this method more satisfactory than those its cost is consequently inappreciable. It has also the obtained by the bottle when the quantity available was advantage over litmus that its solution is less liable to unlimited; I therefore recommend the method without decomposition on keeping. hesitation as applicable to very small quantities of liquid, The quantity of the solution of the indicator, of the as reliable, and as incomparably more rapid of execution strength given above, to be used in each determination is than any other method with which I am acquainted. from one to two-tenths of a cubic centimetre. When
It has often been my custom when ascertaining specific this small quantity is added to a solution containing an gravities for purposes of comparison to cool the oils to alkali to be tested, there is no perceptible colouration as zero Centigrade. This temperature is very easily obtained long as it is alkaline ; but the faintest trace of acid turns by immersing the vessel in fragments of ice placed in a the solution a pale but distinct pink tint, which is easily funnel from which the melted ice-water can readily flow seen if the beaker be placed upon a sheet of white paper. away. It may not be generally known that water in which The best way of applying the test is, after each addi. pieces of melting ice are floating will rarely cool a vessel tion of acid from the burette, to allow a drop of the indito zero, usually not
below two degrees. If a tripod holding cator to fall on the surface of the liquid in the beaker after the funnel is placed over the balance-pan, and a funnel is the contents have been well stirred. . By this mode of selected with a long neck bent nearly at a right angle, the proceeding the indicator is distributed over a smaller water from the melting ice may be discharged into a space, and the reađion is therefore more distina. beaker to one side, while the vessel, holding only a few An immense advantage which this indicator possesses c.c. of liquid is cooled completely to zero with the least over litmus is that it is entirely unaffected by carbonic possible trouble.
acid; the solution need not therefore be boiled, and the For purposes of comparison this arrangement furnishes operation consequently takes much less time; in fact, four results orien of great value in technical operations in operations can be made in the same time as one with which rapidity of execution is often of more importance litmus. That without boiling the solution it competes than that fastidious regard for accuracy which cannot be perfectly with litmus as regards accuracy may be judged over estimated in questions relating to the absolute “con- srom the following table :-. stants of nature."
Determination of Carbonate of Sodium Volumetrically.
One c.c. of the standard sulphuric acid = 0'051176 grm.
Indicator used. ON THE NEW SUBSTITUTE FOR LITMUS.
Cub. centims. obtained.
Orange 3. While engaged in preparing a Supplement to my “Hand- 0:6739 13:15
99.86 book of Chemical Manipulation " I made inquiries in
In order to determine whether the new indicator gave several directions, with the view of ascertaining what improvements had recently been made in the volumetrical sodium, the following experiments were made upon a
as accurate results with ammonia as with carbonate of determination of acids and alkalies. Amongst the per solution diluted to 5 per cent for titration :suns consulted was my friend Dr. Oito N. Witt, who kindly pointed out to me that the "orange 3" of Porrier Determination of Ammonia Volumetrically. formed an excellent substitute for litmus. This new coal. tar derivative was introduced into commerce about two
One c.c. of the standard hydrochloric acid
0'00697 years ago : I believe, however, that its manufacture has grms. of ammonia.
Ammonia heen almost entirely, if not quite, abandoned in favour of
Standard Hydro. Percentage
of Ammonia Indicator used. “Orange 4” or tropæolin 00. This. "orange 3." had, Cub.centims. Cub. centims. obtained. before its introduction into com nierce, been studied inde
Litmus. pendently by Dr. Witt and M. Griess; and M. Lunge, in
22470 ine Berichte der Deutschen Chemischen Gesellschaft, ex
1975 pressly mentions it as an indicator. Its constitution will
19:83 be apparent from its chemical name, dimethyl-amido-azo.
Orange 3. 14 19.85
19*77 berzol-sulphonate of ammonium.
31'30 Lunge has shown that, under certain circumstances
19 83 tropæolin and “orange 3 " are superior to litmus, as they It is obvious, therefore, that the new indicator can be are unaffected by carbonic acid and sulphuretted hydro-employed in the determination of ammonia instead of gen; they are therefore especially valuable in the analysis litmus, and has many advantages over it. of soda residues.
As this matter possesses considerable interest and importance to those who have much to do with the deter- The Banana.-M. Corenwinder.-The total sugar in inination of acids and alkalies, I have subjected this fruit when ripe and sound exceeds 20 per cent, three“orange 3" and litmus to a careful comparison. I fourths of which are crystallisable. When over-ripe the seleded it instead of tropæolin, as it is much more deli. total sugar is reduced to from 16 to 14 per cent, whilst the cale in its reactions.
non-crystallisable sugar rises to II or 12, thus being not Different specimens of litmus somewhat vary in their merely relatively but positively increased. - Comptes sensitiveness to acids and alkalies; that with which Il Rendus.
chloric Acid used.
March 7, 1879.
Examination of Caoutchouc Goods.
sp. gr. 1.828
EXAMINATION OF CAOUTCHOUC GOODS. from different parts, 65.58 per cent. Carbonate on
II'10 per cent. Oxide of zinc, two estimates from
rage sample It was stated some time back (Scientific Notes, Quarterly
ist. 49'98 per cent.
2nd. 49'90 per cent. Journal of Science, April, 1877) that the use of oxide of zinc in the manufacture of caoutchouc nipples for milk.
Lot No. 6. bottles has almost been abandoned. This led to the exam nation of some caoutchouc nipples Carbonate of lime, three estimates :-
Ash, 49°12 per cent. Oxide of zinc, 15:47 per cent. lately imported from England, and supplied by first-class houses. The examination was afterwards extended to
30'21 per cent. samples of tubing supplied for chemists' use, and a few
2nd. 30'22 per cent. other caoutchouc goods.
3rd. 30-45 per cent. Some specimens of chemists' tubing were found to con
Lot No. 7. sist solely of india-rubber and sulphur. Others contained a large proportion of carbonate of lime and a considerable Ash, 48.90 per cent. Two estimates of carbonate of quantity of oxide of zinc, also a little siliceous matter-lime and oxide of zinc :apparently French chalk. Oxide of zinc was present in
Carbonate of Lime. Oxide of Zinc. very large quantity in all the other goods, and siliceous
Per cent. matter never altogether absent.
15'34 The following were more particularly examined :
Certain acids, when brought in contact with these com
which will be fully described further on.
The acids employed were-
Sulphuric acid ..
Acetic acid, containing 63 to 64 per cent anof zinc. The quantity of carbonate of lime in Lots 5, 6,
hydrous acid. and 7 was also ascertained.
They were employed of the above strengths, and also The zinc estimates were made from the material direct much weaker, the dilutions being carried out by volume. by cutting up the latter very small, and adding one piece
The ounce will be understood to mean a fluid ounce. at a time to a mixture of pure carbonate of soda and nitre
The phenomena alluded to arekept in fusion in a porcelain crucible. The mass was 1. Distension of the material from absorption of fluid. dissolved out with moderately dilute acetic acid, the zinc 2. The appearance of small elevations on the surface. precipitated with sulphuretted hydrogen, the sulphide zinc 3. Crimping of the edges. converted into chloride; precipitated with carbonate of These effects appear to be due to the following causes :soda, and weighed as oxide. When two estimates of the same sample were made,
1. The acid has a strong tendency to enter the pores of different weights of material were employed.
the material, in consequence of its affinity for the
lime or oxide of zinc. Lot No. 1.
2. Certain acids (notably acetic acid) not only acts External surface smooth and not easily abraded. Com
solvent on the mineral matters, but also softens the position not quite uniform. Ash, mean of three experi
caoutchouc, rendering it in consequence more easy ments, 46.79 per cent. Oxide of zinc from average sample,
of distension, and at the same time diminishing its 44'14 per cent.
power of contracting after distension. The minute Lot No. 2.
state of division in which the vulcanised rubber is Surface smooth and not easily abraded. Composition
left after disintegration of the mineral matter seems
to favour this action. uniform. Ash, 47'22 per cent. Oxide of zinc, two esti.
3. The acid entering the pores of the softened material mates :
more readily than the solution of zinc or lime salt 43:52 per cent.
formed within the pores escapes from them, disten2nd. 43.68 per cent.
sion follows. These nipples contained a little more clay than Lot No. 1. 4. Small elevations will generally appear on the surface
of the material, because the distension at first is Lot No. 3.
merely superficial. These elevations are also someThese nipples exhibited considerable difference in per. times produced by escaping gas-bubbles. centage of mineral matter. Their surfaces were quite
If a sharp edge is presented to the action of the smooth, but could be abraded rather easily with the finger- acid, crimping of the edge will result, and remain nail.
apparent until the action has proceeded to some
depth below the surface of the material, and dis. Numbers.
tension has in consequence become more general.
The general effects produced by the acids are described
below, and a few examples given of the absorption occa
sioned by acetic acid, &c. Strictly comparable experiLot No. 4.
ments could not be made with the samples at my disposal Surface very rough and easily abraded. Ash, 32'07 per (except perhaps with the chemists' tubing), on account of cent. Oxide of zinc, two estimates :-
the irregular form, unequal thickness, and various degrees Ist. 29'01 per cent.
of elasticity. 2nd. 29°18 per cent.
The appearance which most samples present under the
action of acetic acid is very beautiful, especially if observed Lot No. 5.
with a lens. The phenomenon soon becomes apparent to Surface very rough and easily abraded. Composition the naked eye, except with extremely dilute acid ; but a not quite homogeneous. Ash, estimated from sample cut I lens is required to observe it in the early stage, and to
March 7, 1879. render visible that fine crimping of the edges which con
Action of Nitric Acid. stitutes the only apparent effect produced by very weak acid. With the aid of a good watchmaker's eye-glass I hours. Acidi in 5 also effects decomposition, though
The strong acid reduces the material to pulp in a few have never failed (in numerous trials) to detect the pre much more slowly. A piece of No. I weighing 20 graias sence of i part of anhydrous acetic acid in 3000 parts of was immersed in half an ounce of acid of this strength, water, by immersing a small piece of nipple (weighing and finally examined after eighty hours (slight crimping 2 or 3 grains) from Lot No. 1 in 10 c.c. of the diluted had been observed in the interval). On cutting, decomacid. Distina crimping was observed with the lens after position wa found to have advanced to a considerable twelve to twenty-four hours, when the experiment was performed at the ordinary temperature of the laboratory* which formed a brittle crust.Acid 1 in 10 appeared to
depth, leaving apparently only sulphur on both surfaces, (78° to 82° F.). If the fluid and sample were heated on
have little action beyond dissolving out the metallic the water-bath, in a closed bottle, the reaAion was gene- oxides and slightly softening the caoutchouc, producing rally obtained in two or three hours. It is probable that formic acid will be found to produce effect of this kind could be obtained with acid weaker
crimping and general distension of the material. No the same effect, and that the reaction may be rendered than 1 in 100, and very careful inspection with a strong available as a means of detecting minute quantities of lens was required to observe the faint traces of crimping either acid in the free state in the absence of the other, produced when the most sensitive samples were immersed provided free mineral acids in large quantity are also
in acid of this degree of dilution. absent. I should here observe that all samples of the material
Action of Acetic Acid. will not be found equally sensitive to the action of the acid, a marked difference being observed in some in
Acid of the strength employed in these experiments (or stances between two samples of apparently the same weaker) was found to have very little action on pure composition.
vulcanised rubber. Pieces of tubing (composed of the
latter) left floating in the acid for days appeared quite Action of Sulphuric Acid.
unaltered. On mixing the Auid with water, however, it The strong acid decomposes the material in a few hours. produced milkiness, showing that a small quantity of Some specimens were observed to crimp slightly when caoutchouc had gone into solution. The fact that acetic first immersed, others not at all.
acid has very little action on pure vulcanised rubber ren. Acid 1 in 2t was found to dissolve out oxide of zinc ders its extremely energetic action on the mineralised pretty freely, except from those samples which contained article truly remarkable, especially when it is remembered a notable quantity of carbonate o lime. After twelve that as compared with mineral acids its affinity for bases days' immersion in acid of this strength the elasticity of is feeble. the material seemed but slightly impaired. Not the The strong acid dissolves out the mineral matter very slightest crimping was produced, nor was weaker acid readily, and produces distension so rapidly that no elevafound to occasion it. Acid 1 in 20 dissolved out enough tions appear on the surface of the material, and very zinc from most samples to be readily detected in the fluid slight crimping of the edges is observed. after thirty-six hours' immersion.
Distension, however, although it occurs more rapidly
with strong than with weak acid, is often sooner arrested Action of Hydrochloric Acid.
with the former than with the latter, and long before the A piece of No. I was immersed in about four times its acid has become exhausted. It appears to cease as soon weight of strong acid. In half an hour a notable quan, tion. From this it follows that a weak acid, other things
as the fluid contains a certain proportion of salts in solu. tity of zinc was found in solution. Pieces of No. 1 and being equal, may produce as great or greater distension No. 5 were immersed in excess of strong acid and ex
after a time than a strong one. There are, however, so amined with lens. Numerous gas-bubbles from No. 5, and a few from No. 1. Cut edges acquired a reddish many, circumstances that might influence the result tinge. After two days both samples had acquired a red- (notably the degree of elasticity possessed by the matedish colour all over. Decided crimping. Sulphur had rial) that I should hesitate to accept this as the corred
view without further and more exact experiments than I separated. Some distension of material generally. After four days removed samples from acid, and washed. Elas. have as yet been able to undertake. ticity somewhat impaired. On cutting, it was seen action The following experiments serve principally to illustrate had advanced very far into the material. Original thick the bare fact that very considerable distension does take ness about th inch. A nipple from No. I was cut in two place with the acid, whether weak or strong:lengthwise, and immersed in 2 ozs. acid, 1 in 5.
A piece of nipple from Lot No. 2, weighing 28-72 grs., Aster nine days faint traces of crimping observed with was immersed in 5 ounces of acid, 1 in 300. After a lens. After fourteen days these had nearly disappeared. month the sample was removed, and placed in 5 ounces Removed sample. Washed, dried with towel, and of fresh acid of the same degree of dilution. The sample weighed.
was weighed forty-six days after the commencement of
the experiment. Weight
25-17 grains. Original weight
Weight, 112'18 grs. Apparent gain, 83'46 grs. 24'19
The material could be torn rather easily. A portion ig. 0:98 gr.
nited left a considerable residue of oxide of zinc. Adhering moisture would account for the difference.
Lot No. 2, piece weighing 10-83 grs. Lot No. 6, piece Quantity of oxide of zinc found in one ounce of the fluid, weighing 8-10 grs. Immersed together in 1 ounce of the 0-22 gr. Material seemed uninjured.
strong acid. Weights after twenty-one days : Acid 1 in 20 failed to produce the least appearance of No. 2, 19:80 grs. Apparent gain, 8.97 grs. crimping with the most sensitive samples, the specimens
No. 6, 17:30 grs.
9'20 grs. being kept under the action of the acid for a month, and examined carefully with the lens almost daily.
Lot No. 1.—Nipple cut in two lengthwise. Weight, 23.59 grs., immersed in 2 ozs. acid, 1 in 10. Weight after
fourteen days :* The temperature at which all the experiments were performed' except when otherwise stated.
93.60 grs. Apparent gain, 70'01 grs. 7 One volume of sulphuric acid, sp. gr. as stated, mixed with an equal volume of water. The same for all degrees of dilution, and for Quantity of oxide of zinc fonnd in 1 ounce of the fuid, all the other acids employed.
378 grs. Material very tender.
The Electric Light at the British Museum. March 7, 1879.
IOI Lot No. 1.—Nipple cut in two lengthwise. Weight, I of the Paris Société d'Electricité, assisted by their respec27.89 grs. Immersed in 2 ozs. acid, 1 in 50. Weight tive staffs, have been makirg repeated experiments on the after fourteen days :
practicability of lighting up the British Museum Reading. 138-70 grs. Apparent gain, 110.81 grs.
Room by means of the Jablochkoff system of electrical Quantity of oxide uf zinc found in 1 ounce of the fluid, number and position of the lamps to be used, Mr. Bond
illumination. Having, partially determined upon the 1.43 grs. Material very tender.
decided that on the Monday, Tuesday, and Wednesday of Lot No. 2.- -Nipple cut in two lengthwise. Half im- the present week the Reading-room should be kept open until mersed in 2 ozs. acid, I in 10; the other half in 2 ozs. seven o'clock, so that the holders of reading-tickets might acid, 1 in 50. Original weight of half in acid i inic, have the opportunity of practically testing the value of the 19-97 grs. Weight after fifteen days :
welcome innovation. On Monday evening, accordingly, 73630 grs. Apparent gain, 53'33 grs.
about two hundred readers remained behind after the Original weight of half in acid 1 in 50, 15*19 grs. six o'clock, the twelve Jablochkoff candles in shades of
usual hour for closing, and when, at a few minutes before Weight after fisteen days :
opal glass suddenly burse into light, those present forgot 72.80 grs. Apparent gain, 57-61 grs.
for the moment that they were in a building devoted to The halves presented originally very nearly, if not quite, silence and study, and evinced their approval of the efforts the same extent of surface, the difference in weight being of the Museum officials on their behalf by breaking into due to difference in thickness. After being acted on by a burst of applause, a sound which we will venture to say the acid, the material in both experiments was found ex- has never before been heard beneath Sir Antonio Panizzi's tremely tender.
famous dome. After this considerable distension fuid escapes so ra- Roughly speaking the Reading Room is a circle, ninepidly from the pores of the material, on removal from the teen-twentieths of which are devoted to the public, the acid, that the weight obtained only approximately repre. remaining twentieth forming the passage into the Library. sents the amount of absorption that has taken place. In the centre there are three circular desks, the inner one
The amount of mineral matter dissolved out must also being used for the delivery and return of books, and the be taken into account. If left to dry these distended two others, which are breast high, for stacking and using samples gradually contract to about their former dimen- the voluminous catalogues. From these run radially sions, but never recover their elasticity unless the action nineteen desks divided lengthways by a partition, and of the acid has been only slight.
lettered from A to T both inclusive, but missing Q, sevenIn reference to the phenomena of crimping, &c., by far teen of which are double, the two end ones being single. the finest effects are produced by a dilute acid, say í in At present the first four, A, B, C, and D, are each illu300. The result obtained in the following experiment minated by a Jablochkoff lamp, placed on a standard (one out of a very large number tried) will serve to illus- fifteen feet high, fixed exactly in the middle of each desk, trate the action of acid of this strength on a fairly sensi- being sustained by the longitudinal partition which sepa. tive sample of the material :
rates the readers, the remaining fifteen desks being lighied Lot No. 1.-Nipple with top cut off ; weight 17.9 grs.
by seven lamps placed alternately. The remaining lamp Lot No. 6.-Piece of tubing cut off ; weight 9 gis.
is placed in the centre of the room, and lights the desks Immersed both in oz. acid, 1 in 300. Ëxamined after of the Superintendent and his assistants. The general twelve hours:
opinion amongst the readers appears to be one of unani. No. 1.—Decidedly but finely crimped on cut edge, quite mous approbation of this mode of lighting. We have
apparent to naked eye. Surfaces slightly raised. A thoroughly tested the matter in a practical manner by few bubbles.
reading, writing, tracing, drawing, and painting at one of No. 6.-Edges slightly crimped. Requires lens to see
the first four desks as well as at those which are only distinctly. Surfaces very slightly raised.
lighted alternately. In the first case there is abundant After thirty-six hours :
light for comfortable working at any part of the four desks, No. 1: - Beautifully and finely crimped. Base ring but in the latter a reader sitting at either end of the illu
looks like fine sponge. Exterior surface covered minated desks has to twist himself round most uncom. with small round elevations, beautifully regular. | fortably to get out of his own shadow. We venture to Interior surface very slightly raised. No bubbles.
think, therefore, that for the new mode of lighting to be No. 6.-Edges rather strongly crimped. Surface slightly thoroughly satisfactory to all, the whole of the nineteen raised. No bubbles.
desks must each be provided with a lamp, thus rendering Very fine effe&s can be obtained with much weaker the imitation of daylight as perfect as need be.
It is agreed on all hands that the light is mellow and acid than 1 in 300, provided the material is sufficiently sensitive. With most of the nipples I have obtained resoft, and most agreeable to work by. Now and then, it is action in acid I in 2000 (equal to about i part anhydrous ally it waxes and wanes slightly, but these defeats will no
true, there is a sudden flutter in the light, and occasion. acid in 3000 parts of water). With sample Lot No. 5 doubt disappear when everything is in full working order. acid 1 in 300 hardly produced any effect. Old samples that have lost their elasticity to a consi- machine of the latest construction, worked by a Robey
The source of electricity is a 20-light duplex Gramme derable extent will be found equally inactive. Falmouth, Jamaica,
portable engine of 16 horse-power nominal. There are January 22, 1879.
four circuits of five lamps, but only sixteen are used at present; that is to say, twelve in the Reading Room, one in the Entrance Hall, one under the portico, and two in
the machine and engine-shed. The machine and its THÈ ELECTRIC LIGHT
engine are placed outside in a wooden erection at the IN THE BRITISH MUSEUM READING-ROOM. north-west corner of the Museum buildings, about 200 yards
distant from the Reading Room.
The four candles used in the lamps at desks M, O, R, Last Monday will henceforth be looked upon as and T are of an improved kind lately invented by one of interesting point of departure in the history of the British M. Berly's assistants, and are now tried for the first Museum Library, for on that day its manifold treasures were time. They differ from the ordinary Jablochkoff candles for the first time thrown open by night as well as by day in the insulating material between the carbons being reto those entitled to use them.
placed by a composition which we suppose must be a For the past three weeks Mr. Bond, the Principal feeble conductor. Extinction, except for a moment, is Librarian, and M. Berly, C.E., the London representative i therefore impossible. The use of the carbon tridge for