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And every other Mercurial Preparation.

BISULPHITE OF LIME, TETRACHLORIDE OF CARBON.
Oxysulphuret of Antimony, Glacial Acetic Acid,

LIQUOR AMMONIÆ,
SULPHIDE OF IRON,

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PERCHLORIDE OF IRON,

SULPHITE AND HYPOSUL

PHITE OF SODA,

CHEMICAL NEWS,
May 30,1879.

TOWNSON & MERCER,

89, Bishopsgate Street Within,

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LONDON.

Wholesale and Export Dealers and Manufacturers of

CHEMICAL & SCIENTIFIC APPARATUS
PURE CHEMICALS, &c.,

For Analysis and the general Laboratory Use of Manufacturers
and Professors of Universities, Schools, Mines, &c.

Now ready,

TOWNSON & MERCER'S COMPLETE CATALOGUE 0 Chemical and Scientific Instruments, Pure Chemicals &c. Demy 8vo. Illustrated with upwards of 800 Woodcuts. Price 2s. 6d. post free.

PHOSPHATES OF SODA AND PATENTS. Mr. Vaughan, F.C.S., British,

AMMONIA,

ETHERS,

BROMIDES,

IODIDES,

SCALE AND GRANULAR PRE-
PARATIONS.

ALSO,

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Foreign, and Colonial PATENT AGENT. Special attention given to Inventions relating to Chemistry, Mining, and Metallurgy Guide to Inventors" Free by Post.-Offices, 67, Chancery Lane London, W.C., and 8, Houndgate Darlington.

MINERALOGY AND GEOLOGY. NEW LIST of Collections of Minerals, Fossils, and Rocks, with prices. New List of Minerals for Chemical Purposes, Manufactures, and Research. New List of Varieties of Rocks. New List of Prices and Sizes of Cabinets for Natural History and other purposes. New Catalogue of Secondhand and New Books on Geology and Kindred Sciences. New Supplementary List of Books. New List of Sections of Rocks and Minerals for the Microscope. New List of Prices and Patterns for Geological Hammers. New List of Blowpipe Cabinets, Apparatus, and Materials. Also Implements and Appliances for practical work in Geology and Mineralogy.

Post free on application to JAMES R. GREGORY, Geologists and Mineralogists' Repository, 88, Charlotte Street, Fitzroy Square, London.

Water-Glass, or Soluble Silicates of Soda

and Potash, in large or small quantities, and either solid or in solution, at ROBERT RUMNEY'S, Ardwick Chemical Works, Manchester.

ORGANIC

RGANIC MATERIA MEDICA.
BY DR. MUTER.

Analytical Chemists will find this a concise and yet complete book of reference for the isolation and examination of the active principles of drugs. Special appendix on the microscopic characters of the starches in food and drugs. Copious index and qualitative courses or resins, &c.

Published by W. BAXTER at the Office of the South London School of Pharmacy, Kennington Cross, S.E., and sold by Messrs. Simpkin and Marshall and Messrs. Baillière, Tindal, and Cox:

IMPORTANT TO SULPHURIC ACID MANUFACTURERS.
NORRINGTON'S PATENT.

In

In the ordinary method of Manufacture, at the time of charging the Kilns, a considerable escape of gases takes place. This is attended with proportionate loss of Sulphur, and with much inconvenience to the workmen, as well as annoyance to the vicinity of the Works. This may be entirely avoided by the adoption of C. Norrington's patented invention, which can be applied at moderate cost to existing Plant, as well as in the erection of new Works. It may be seen in full operation on extensive Plant at Messrs. C. Norrington and Co.'s Chemical and Manure Works, Cattedown, Plymouth, where the fullest information may be obtained, with terms for license.

CHEMICALS.-Complete Fittings for an

Amateur Laboratory. Open Cabinet, eight feet and a half high by nine feet long; Quantity of Chemicals in stoppered

Becker's Complete Lists forwarded by post on receipt of 1d. stamp, bottles; Apparatus, including two large Bunsen burners and or free on application.

JAMES WOOLLEY, SONS, & CO.,

69, MARKET STREET, MANCHESTER,

DEALERS IN

CHEMICAL AND SCIENTIFIC APPARATUS
CHEMICAL REAGENTS, &c.,

FOR THE USE OF

ANALYSTS, SCIENCE TEACHERS, AND MANUFACTURers.

Price Lists on application]

stoves, with flue pipes. Price as they stand in Plumstead £15; can be seen by appointmeut-Address, P. L. 40, Deacon's Advertisement Offices, Leadenhall Street, E.C.

TO CHEMISTS AND DRUGGISTS.

The Shop, 140, Leadenhall Street (in which a

Chemist's Business has been successfully carried on for nearly 180 years), to be Let on 21 years Lease (in consequence of existing Tenants retiring from business), with possession on July 10, 1879. For further particulars apply to Messrs. Jones, Lang, and Co., 5, King Street, Cheapside, E.C.

TO MANURE MANUFACTURERS.

FOR SALE. About 150 tons Monthly of

Woollen Shoddy; free from grease; containing nitrogen near Manchester.

MURIATIC ACID Nine Carboys for Dis-equal to from 5 to 10 per cent ammonia.-Apply to David Shaw and

Cheap.-Apply to W. J. Mott, Rainham, Essex.

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I HAVE lately been engaged in studying the spectrum of sodium under new experimental conditions. In anticipation of a detailed communication I take leave to state that the vapour given off from the metal after slow distillation in a vacuum for some time shows the red and green lines without any trace whatever of the yellow one. Hydrogen is given off in large quantities, and at times the C line and the red "structure" are seen alone. After this treatment the metal, even when red hot, volatilises with great difficulty.

acid? Second, can selenium replace sulphur as a constituent of albuminous bodies? If it were possible through the agency of the organs of plants to effect the replacement of an element not merely in an organic, but in an organised body, the achievement would be one of the greatest importance. Absolutely nothing has been done in the way of effecting the synthesis of new bodies by means of the wonderful combining powers which are exerted in the vegetable mechanism.

The difficulty with which compounds of selenium analogous to the organic bodies containing sulphur are prepared, and the instability of so many of them, are facts which deter one from feeling sanguine as to the possibility of effecting the synthesis of organised selenium bodies by means of plants; still the attempt is worth making. Much more hopeful is the chance of replacing sulphuric acid by selenic acid. I am of this opinion from the results of an experiment which I made several years ago upon a very small scale, and which I never published up to the present, every year intending to repeat upon a larger scale. The experiment was as follows:-A sod was taken from a field in which a crop of the so-called artificial grasses (which are chiefly leguminous plants, and not grasses at all) was just peeping over ground. The sod was 2 feet in depth, 3 feet in length, and I foot

PRELIMINARY NOTE ON THE ABSORPTION OF wide. It was placed in a box, and one-half of the plants

SELENIUM BY PLANTS.*

By CHARLES A. CAMERON, M.D., Professor of Chemistry and Hygiene, R.C.S.I.

THE subject of the possibility of replacing some of the elements found in plants by other elements of the same atomicity has not engaged the attention of British chemists; but on the Continent a few attempts in this direction have been made, generally with but little success. For example, Berner and Lucanus vainly attempted to replace ferric oxide (Fe2O3) in plants by the manganese analogue of that compound (M2O3). Experiments made with the view of substituting sodium for potassium in plants have invariably given negative results. The possibility of completely replacing an element in plants by another was, however, proved by me in a paper read before this Society in 1863. I found that rubidium was capable of taking the place of potassium. It may be that certain bodies, though not capable of completely replacing other substances in vegetables, may be partially substituted therefor. The varying proportions of sodium and potassium found in the ashes of plants would seen to indicate such a partial replacement. As a rule, whenever potassium is sparsely present in the ashes of a plant, sodium abounds therein, and vice versa.

The analogy between sulphur and selenium suggests the

possibility of the latter wholly or partly replacing the former as a constituent of vegetables. Sulphur exists in plants on two conditions, namely, as a constituent of sulphuric acid, and as an ingredient of albuminous and certain oily bodies. Sulphur is only taken up into the mechanism of plants in the form of sulphates, such as, for example, calcium and sodium sulphates. By the partial deoxidation of these sulphates, sulphur is procured by the plant and employed in the elaboration of its albumen, casein, and other albuminoids. The results of the interesting experiments of Arendt render it probable that sulphur is both oxidised and deoxidised in the plant at different periods of its development. Thus, after blossoming the oat was found to contain more sulphur trioxide than before the ears of the plant had formed; and whilst the sulphur trioxide disappeared altogether from the lower part of the stem, it increased largely in the leaves and in the plant at large.

Now, there are two problems to be solved in relation to the substitution of selenium for sulphur in plants. First, can selenium in the form of selenic acid replace sulphuric

Paper read before the Royal Dublin Society, May 19, 1879.

were watered twice a week with a weak solution of potassium selenate (K2SeO4). During four weeks the total quantity of potassium selenate applied to the plants amounted to 20 grms., which comprised my whole stock of the article.

Now, this experiment was merely a tentative one. First, to ascertain whether or not selenic acid would act injuriously upon plants. Secondly, to discover whether or not the selenic acid could partly replace the sulphuric acid, or rather could be taken up into and permanently retained by the plant. With respect to the action of the selenate, I could not perceive any difference between the plants to which the salt had been applied and those to which it had not. I came to the conclusion, therefore,

that selenic acid applied at least in small quantities did not injure plants.

The next step was to ascertain whether or not the selenic acid had been partially absorbed. The plants were accordingly partially dried, and boiled in strong nitric acid until thoroughly destroyed. The solution was evaporated to dryness, and the residue was treated with dilute hydrochloric acid, which dissolved it nearly completely. The solution was concentrated and mixed with a saturated solution of sulphurous acid, whereupon the liquid assumed at once a deep blood-red colour, from the

separation of selenium.

Before the plants were partially dried they were carefully washed, in order to separate any traces of selenate which might have adhered to their surface. The applica

tion of the selenate solution was discontinued for a fort

night before the plants were taken up.

I think this experiment proves that selenic acid is not injurious to plants when used in small quantity, and that the acid is taken up and retained by plants, or at least of did not prove whether or not there was a partial replacecertain varieties of plants. The experiment, however, ment of sulphur trioxide by selenium trioxide or of sulphur by selenium. Having lately become possessed of large quantities of selenium compounds, I proposed to grow plants in soil or water free from sulphur in any form, but supplied with potassium and ammonia selenates. Should the results of this proposed experiment prove interesting I shall do myself the honour of submitting them to the Society.

Proportion of Carbonic Acid in the Atmosphere. J. Reiset.-The air contains in 10,000 parts 2'942 parts of carbonic acid by volume. The most extreme variations have not exceeded 3 parts in 10,000.-Comptes Rendus.

244

Composition of the Ash of Wheat-Bran.

ON AURIN." PART II.

By R. S. DALE, B.A., and C. SCHORLEMMER, F.R.S.

SOME time ago we read a paper before this Society, in which we stated that on heating aurin, C19H1403, with an excess of aqueous ammonia, it is converted into pararosanilin, CiH17N3.t There ought to exist two compounds standing intermediate between aurin and rosanilin, viz., C19H15NO2 and C19H16N2O, as the action of ammonia probably proceeds in three stages :

C19H1403+NH3=C19H15NO2+H2O,

C19H15NO2+ NH3=С19H16N2O+H2O,

C19H16N2O+NH3=C19H17N3+H2O.

We have made a very large number of experiments for the purpose to get hold of one of these intermediate products, and have at last succeeded in obtaining one, probably the first, in beautiful crystals; it dyes on silk and wool a rich red, and as the commercial red aurin, which is obtained by the action of ammonia on common or yellow aurin, has also been called peonin, we will retain this name for our compound. It is formed by heating aurin with dilute ammonia to 100° C. for some weeks. A body dyeing exactly the same shade, and therefore undoubtedly the same compound, is obtained by passing for a few hours ammonia gas into a solution of aurin in boiling amyl alcohol.

As we encountered many difficulties in the preparation of peonin, we thought more definite results might be obtained by using a compound ammonia, and therefore tried the action of methylamin on aurin. Methylamin is now a commercial article, being obtained from beetrootmolasses by M. Vincent's method, which Dr. Roscoe described to this Society some weeks ago; he was kind enough to present it with the methylamin required for our experiments.

On heating the two bodies together for a few hours, the deep red colour of the liquid became much paler, and a brown deposit was formed in the tubes, which on examination was found to be trimethyl-para-rosanilin, which is formed according to the equation—

C19H14O3+3(CH3) NH2=C19H14(CH3)3N3+3H2O. We have dyed with it, as well as with the other bodies mentioned in this paper, silk, wool, and mordanted cotton, and beg to submit these samples to your inspection. We have already proved that by acting on aurin with aniline the final product consists of triphenyl-pararosanilin, and thus shown that the whole host of bodies known as the aniline colours can be obtained from phenol.

ON THE

COMPOSITION OF THE ASHES OF WHEATBRAN, BURNED UNDER A STEAM-BOILER. By S. F. PECKHAM.

SOME time ago, at a meeting of the Minnesota Academy of Natural Sciences, a substance was handed me by someone present with the remark that it was the fused ashes of wheat-bran, burned under a steam-boiler. The material was nearly pure white in colour and vesicular in structure, resembling more nearly some specimens of Cooper River phosphate than anything else that I remember. Wishing to learn its composition I submitted it for analysis to Miss Cora J. Brown, then a student in the University Laboratory. Miss Brown had already proved herself a very careful and skilful manipulator, and she conducted the analysis with exquisite neatness and patience, and with the most gratifying results.

Paper read before the Manchester Literary and Philosophical Society, April 1, 1879.

Mem. Lit. Phil. Soc. (3), vi,, 248,

CHEMICAL NEWS, June 6, 1879.

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No carbonic oxide (CO2) was present. The very small proportion of chlorine is doubtless due to the high temperature to which the ash had been subjected-a tempermay therefore properly be considered an ash residue conature sufficiently high to completely fuse it. The substance sisting of its less volatile portions. The presence of free phosphoric acid in such a compound may be questioned; perhaps also the presence of normal magnesium phosphate. It must be remembered, however, that it is scarcely a supposable case that the phosphates in the bran are acid phosphates, producing pyrophosphates when burned; and while it would appear more probable that the albuminoid phosphorus contained in the bran would burn into phosphoric oxide and escape in the smoke, it is not a necessary supposition, especially when the results of analysis show that there is more phosphoric oxide present than is sufficient to form normal phosphates with the available bases. I have therefore assigned the composi tion given above as the most satisfactory interpretation of the results.

Laboratory of the University of Minnesota,
May 7, 1879.

Heat attending the Formation of Cyanogen.—M. Berthelot.-The mean heat evolved on the combustion of cyanogen, calculated for its equivalent C2N=26, is 1323 calories. In its formation heat is absorbed to the extent of 38.3 cals. Hence, like acetylen and nitric radicals, it is a body formed with disappearance of heat. oxide, substances which play the part of true compound -Comptes Rendus.

NEWS

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THE flue dust which was examined was taken from a short flue leading from pyrites kilns in which Spanish cuprous pyrites were burned. As the flue in question was an iron tube not more than 2 or 3 yards long, anything that condensed in it must have done so at a very high temperature; and that probably accounts for the very small quantity of selenium found, as that metalloid is found in appreciable quantities in the sulphuric acid manufactured from these pyrites.

The greater part of the flue dust consisted of compounds of arsenic, antimony, lead, copper, and iron; but it is only the thallium, tellurium, and selenium that this note is concerned with.

Thallium.-The flue dust was treated with sulphuric acid for the extraction of the thallium, which was precipitated as chloride. The chloride was re-dissolved and re-precipitated twice, and then reduced to the metallic state with cyanide of potassium. One sample of flue dust, treated thus, gave about o'05 per cent of thallium, while in another case the amount obtained did not exceed o'002 per cent.

Tellurium. The insoluble matter left after the above treatment with sulphuric acid was boiled in a solution of caustic soda. The solution was filtered off, acidified with hydrochloric acid, boiled, cooled, saturated with sulphurous acid, and boiled again, when the selenium and tellurium were precipitated. This precipitate was collected, dried, and then fused with cyanide of potassium in an atmosphere of coal-gas. The fused mass was allowed to cool, and then dissolved in warm water saturated with coal-gas, and through which a stream of coal-gas was kept continually passing, on a filter. The telluride of potassium thus dissolved passed through the filter exhibiting its characteristic claret colour, which it, however, immediately lost, becoming colourless, and precipitating tellurium unless a stream of coal-gas was kept passing through the filtrate also.

The amount of tellurium found was about o'002 per cent of the matter undissolved by sulphuric acid in the treatment for thallium. The amount of selenium did not exceed o'oor per cent.

CHEMICAL JOTTINGS.

By H. R. PROCTER.

1. Weselsky's Reaction for Phloroglucin. THIS reaction is described in the Chemical Society's Journal, 1876, i., 964, and consists in the production of a cinnabar-red precipitate when a trace of phloroglucin is added to a solution of nitrate of aniline or toluydin containing a little nitrite, and the mixture allowed to stand

some hours.

It is known through the researches of Hlasiwetz (Ann. der Chemie, cxliii., 290) and others, that many tannins when heated with dilute sulphuric acid are resolved into glucose and peculiar red bodies which we may call phlobaphenes. These again, when fused with potash, are decomposed into protocatechuic acid and another body, which in some cases is a fatty acid, and in others as the species of sugar known as phloroglucin.

To be able to recognise these phloroglucide tannins without the tedious process of separation noted above would be an important aid to the classification and qualitative

* Read before the Chemical Section of the Glasgow Philosophical Society.

1879.

Read before the Newcastle-upon-Tyne Chemical Society, March 27,

identification of these complex bodies; and it occurred to me that possibly they might give Weselsky's reaction in their unaltered condition. To test the matter, I mixed in test-tubes 5 c.c. water, I c.c. of a saturated solution of nitrate of aniline (probably containing toluydin), and I c.c. of very dilute solution of potassic nitrite, and added to each tube I c.c. of solutions containing as nearly as possible 5 grms. per litre of the following bodies:-(See Table, next page.)

In

In five minutes most had become yellow, gambier, and oak, and churco barks deeply so, and in an hour oak and churco barks had deposited a deep red precipitate. twelve hours all had precipitated more or less, but the glucose and sugar yielded only traces. The gambier, which contains catechin, a well known phloroglucide, gave a fine deep red precipitate, and oak and churco barks, which very probably contain phloroglucin, gave precipitates of which the lower part was equally bright.

It seems evident, therefore, that phloroglucides in combination may yield this reaction, but that many other bodies also give reddish-brown precipitates which may easily lead to mistaken conclusions. When more dilute solutions are used the same facts are observed, but the red precipitate is more distinct from the rest. Some precipitate was even obtained on long standing from aniline nitrate and potassic nitrite alone. The precipitates seem remarkably stable, being unaltered by solution of iodide, dilute acids, ammonia, sulphurous acid, or sulphide of sodium.

The yellow supernatant liquid, if acidified and exposed to the air, becomes bright crimson, and sometimes deposits minute crimson double-refracting acicular crystals. It is turned yellow by ammonia and its colour restored by acids.

Watts states that pyrocatechin gives Weselsky's reaction.

The churco bark to which I have alluded is the product of the Oxalis gigantea of Chili, and contains a red tannin equal in amount, by Löwenthal's test, to from 25 to 26 per cent. quercitannic acid. The sample in my possession was kindly supplied by Messrs. Machado, of Glasgow. I have made some preliminary experiments as to the application of Wiesner's test for woody fibre-the purple colouration produced on moistening it with solution of phloroglucin and then with the hydrochloric acid (Chemical Society's Journal, 1878, p. 809)-to the converse detection of phloroglucides. Deal shavings moistened with solution of gambier gives it strongly. I hope to pursue the subject

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In packing my chemicals for removal to a new laboratory, I came upon two bottles of this solution, probably five or six years old, which had formed an orange-yellow deposit on the sides. Having recently read of a case, to which I am sorry that I cannot at the moment refer, in which a hottle with a similar deposit had exploded violently on being broken, I determined to try the experiment at once, lest it might try itself under more dangerous conditions. The bottles were thrown against a wall, and one exploded with a large puff of flame and white smoke: the other gave a slight flash, and smoke which smelt rather of phosphoretted hydrogen than of phosphoric acid. It is evident that some new and spontaneously inflammable compound had been formed, since the fresh solution only inflames after some minutes, when the carbon disulphide has had time to evaporate, and fails to do so at all when the temperature is very low. In the present case the thermometer was below freezing-point, and combustion was instantaneous. Phosphoretted hydrogen is out of the question, unless moisture had found its way into the bottle.

but think it well to put it on record as a caution, since Of course I can claim no originality ir. this observation,

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the reaction might easily give rise to a dangerous their carefully conducted experiments. One great point

accident.

III. Determination of the Free Acid in Tan Liquors. Tan liquors usually contain, in addition to tannins, gallic acid, catechu, and other bodies of very feeble acid properties, a certain portion of acetic and other fatty acids, and frequently free sulphuric and hydrochloric acids, which have been purposely added. For technical purposes it is often desirable to determine these stronger acids, which are capable of dissolving lime and swelling the tissue of hide in presence of tannin, &c., which have the opposite effect. This cannot be done by an alkaline solution and litmus, since the tannins are immediately oxidised in

alkaline solution, giving rise to dark coloured products, A simple and sufficiently accurate method for technical purposes is to use lime-water as the standard solution, adding it to the clear filtered liquor in a beaker until permanent turbidity is produced. This point is easily recognised by holding the beaker over a printed page. The end reaction, of course, depends on the fact that calcic tannates are soluble, or more probably cannot be formed in the presence of a free and stronger acid. I have not attempted to determine exactly what acids are estimated by this process, the mixture is complex, and the amount of lime which they are capable of dissolving is the essential point in practice.

which obscure the end-reaction.

which has been decided on the Victoria Embankment is that the steadiness of the light is in a great measure dependent on the regularity with which the motive power is supplied to the electric machine. In the present case this uniformity of power was secured by the use of a specially constructed 20 horse-power engine, provided with an automatic governor of extraordinary sensitiveness, the whole being supplied gratuitously for three months by Messrs. Ransomes, Sims, and Head, of Ipswich.

The experiments upon which Messrs. Bazalgette and Keates's figures are founded began on January 24th, and were continued until February 5th, Sundays excepted, or, in other words, for twelve nights,-the engine being lighted. The mean daily cost of working the engine, indriven for 5.5 hours each night, the whole 26 lamps being cluding wages, was found to be £1 9s. 84d., or 3°24d. per lamp per hour. The cost of the whole plant was £1280, but a smaller engine would be quite sufficient for the purpose; the capital required, therefore, might be reduced to £990.

The accurate estimation of the amount of light given off by the electric arc and ignited carbons is," say the Reporters, "a matter of great difficulty, so much so that the best results which have been obtained can only be looked upon as fairly approximating to the truth." This difficulty arises from two causes: first, from the difference in colour between the electric light and any standard of light at our command; and secondly, the fluctuating character of the electric light. The photometrical experiments made on the Embankment were-rst, on the naked light;

REPORT ON THE EXPERIMENTS WITH THE 2ndly, on a light with an opaline globe; and 3rdly, on a

ELECTRIC LIGHT

ON THE VICTORIA EMBANKMENT.

THE joint official report of Sir J. W. Bazalgette, the engineer, and Mr. T. W. Keates, the consulting chemist of the Metropolitan Board of Works, has recently been made public, and is a model of what such a report should be.

For the first time in the history of the electric light, as applied to street illumination, we have a series of data laid before us about whose accuracy there can be no doubt. Hitherto such reports have emanated from either gas-managers or electricians, whose interests-wrongly we think-have been held to be opposed to each other; hence the singular discrepancies in the data which have been issued up to the present time. It must be perfectly understood that we in no way intend to make the slightest imputation against the honour of the authors of these reports; but when one side tells us that the electric light is cheaper than gas, and the other that gas is cheaper than the electric light, we can only account for the discordance of opinion by supposing that the reporters' judgment must have been unconsciously influenced by their anterior convictions. In the present instance we have the conclusions of two eminent public officials, who have no other interests to serve than those of the community at large, and who are wholly independent of the advocates or opponents of either system of lighting.

We regret that we cannot follow the reporters through all the elaborate series of calculations which they have laid before us; we can only gather a few of the results of

light with a granulated globe. The measurements were made with an ordinary bar photometer, fitted with a movable screen with a star disk.

The standard unit of light which was used was a sperm oil lamp, specially constructed for the purpose by Mr. Sugg, and fitted to the photometer by a peculiar balance, by which the necessity for removing the lamp during the course of any number of experiments is obviated. The unit of light given by this lamp was equal to 16 Parlia made on each experiment, both with open and shaded mentary standard sperm candles. Twenty readings were lights, that is to say, 160 on the naked light, 24 with the opaline globe, and 16 with the granulated globe. The following are the mean results obtained in these experi

ments:

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The loss of light produced by the opaline globes is 59 per cent; by the granulated globes, 29.9 per cent.

Taking the above data as approximately correct, the gross output of light from the twenty Jablochkoff candles amounts to 7562 candles, nearly 60 per cent of which is absorbed at once by the opal globes. There are also two other sources of loss: first, from the greater thickness of the opal glass in the lower third of the globes; and secondly, from the fact that the most favourable direction for the projection of the light from the Jablochkoff candle is upwards, there being an actual diminution of light horizontally, and still more so downwards.

On the 14th and 15th of March a very important expe

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