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most of the phenomena arising from heat and combustion. Should there be a theory advanced as original accounting for the action of flame, fire, combustion, &c., upon electromagnetic laws, they have all been anticipated, and they will only be a revival of rejected theories, but in a further stage of development than they have hitherto been. The author above quoted imagines there to be an electric atmosphere surrounding all bodies, and it is by disturbing their equilibrium that the phenomena of electricity are produced, and he instances the fact that, to cause the electricity of an electric (plate) machine to be made manifest, it must be excited by friction which the conductor conveys to the Leyden jar, and therefore the plate is for the time being negative; but the equilibrium of its electric atmosphere is restored either by the earth or surrounding bodies. It is well known that when the machine is insulated upon a glass stool, the evolution of electricity is not so abundant as when in communication with the earth. The plate, therefore, only serves the place of a medium between the rubber and the earth; for what is abstracted from the plate is supplied by the earth.

Red Lion Street, E.C., October 25, 1865.

JEREMIAS.

Suggestion of a New Method of Barometric Registration.

more difficult case, the practicability of giving a suffici-
ently accurate motion to the rod and drum, where the
correctness of registration would depend on this; also the
variation of interval introduced by the difference of time
taken up by the movement of the rod before coming into
contact with the mercury; correction for depression, &c.
Should any one think this suggestion worthy of their
notice, and succeed in practically carrying it out, I should
be glad to hear from them, and would only ask whatever
credit may be due for the invention.
I am, &c. EDWARD CROSSLEY.

Park Road, Halifax.
P.S.-I find that Negretti and Zambra employ a fixed
contact-point for adjusting the level of mercury in the
trough; but I have nowhere heard of motion being given
to a contact-rod for purposes of registration.

MISCELLANEOUS.

Science Examinations of the Committee of - The following are the on Education, Council

By careful deductions, the phenomena of ignition can be made simple and easy of comprehension, and it is from the laws of electric equilibrium and disturbance that the de-results of the reports of the examiners on the examination duction must be drawn. I have already exceeded the which took place throughout the United Kingdom during limits of a letter, and cannot enter further into a considera- the month of May last, comparing the numbers of candidates in 1864 with those of 1865. In geometrical drawing tion of all the facts tending to support the electric theory they have increased from 312 to 608; in machine drawing, of ignition; but should you favour me, as you have my from 185 to 293; in building construction, from 55 to 74: former letters, I shall in a future communication resume from 43 the subject, and hope to bring some very cogent proofs of in mathematics, from 78 to 182; in theoretical mechanics, to 94; in applied mechanics, from 26 to 50; in my assertions. magnetism and electricity, from 269 to 291; in inorganic chemistry, from 851 to 946; in geology, from 164 to 170; in animal physiology, from 479 to 548; in zoology, from 174 to 182; in vegetable physiology, from 121 to 229; in metallurgy, from 70 to 93; in navigation, from 99 to 103; in nautical astronomy from 70 to 82; in steam, from 63 to 76; and in physical geography, from 70 to 121. In five of the subjects there has been a slight decrease-viz., in acoustics, light, and heat, from 253 to 244; in organic chemistry, from 142 to 139; in mineralogy, from 28 to 19; in systematic botany, from 70 to 33; and in mining, from 22 to 15. The progression during the last five years has been as follows:-In 1861 there were 878 candidates; in 1862 there were 1943 candidates; in 1863, 2671 candidates; in 1864, 3644 candidates; and in 1865, 4593 candidates. The total number of prizes given in 1865 was 1482, against 1318 in 1864. The number of medals awarded in 1865 was as follows:-8 gold medals, I certificate instead of a gold medal, 17 silver medals, 6 certificates instead of silver medals, 22 bronze medals, and 12 certificates instead of bronze medals. The following were the successful candidates for the Royal Exhibitions awarded after the result of this examination:-For those at the Royal School of Mines, London-Thomas Jones, Manchester. For those at the Government School of Woolwich; Edward Collens, Bristol; John A. Griffiths, Science, Dublin-Frank Clowes, London; James Craik, London; John Conolly, Bandon; W. B. Leonard, Drogheda.

To the Editor of the CHEMICAL NEWS. SIR,-Though I do not doubt that photographic registration of the barometer is capable of great accuracy, yet it seems to me that there is still another method by which, perhaps, as great accuracy may be obtained, without the uncertain friction of a float, less liable to get out of order, and, consequently, more useful in the hands of the public. The principle is that of an independent, vertically-moving rod, registering instantly the point at which it comes into contact with the mercury of the barometer by thus forming an electric circuit. As an ordinary modification, I would suggest that every hour the rod should be lowered through the whole range of the barometer by clockwork. On the formation of contact, an electro-magnet, by means of an armature, would cause a point carried along with the rod to be indented into the registering paper, or other material, on a revolving drum similar to those already constructed for the purpose, to go for a week at a time.

For more accurate purposes still the drum might be made larger, say five inches in diameter, and fourteen inches long, and divided vertically into two inches for every day. In this case the drum would have to be moved up on its vertical axis every time, through a division equal to the interval of registration,-one-twelfth of an inch for one hour, for instance-and the recording-point would remain stationary, except when acted on by the magnet. At the hour, a simultaneous motion would have to be given to the rod and the drum,-the first vertical and descending, the other horizontal and revolving-so that one inch and a-half of the one would be equal to fifteen inches circumference of the other. The electric current, by means of the magnet as before, would, at the instant of contact, record the point at which this took place, and, consequently, the height of the barometer at that time.

As I have no time for working out the idea, I have not gone into any mere practical details of construction or slight causes of variation to be allowed for, such as best form of battery; manner of communicating vertical motion to the rod; recovery of its position; effect of duration of contact; withdrawal of contact; or in the second and

- Fire-Damp in Coal Mines.—Mr. G. F. Ansell has sent to a contemporary the following account of his mode of applying the law of diffusion to the indication of the presence and amount of fire-damp:-" Gases would appear to be formed of minute atoms, which have motion amongst themselves, rapid or slow, in proportion to the density of the gas experimented upon. This motion of the atoms is not confined to each individual gas, but the atoms of one gas pass freely through and amongst the atoms of another gas, thus producing a perfect mixture of any two gases which are so circumstanced as to admit of the requisite The atoms of a gas are not arrested in their motion. motion by septa of porous substances-that is, substances impervious in the ordinary acceptation, but not absolutely

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and 10 per cent. of gas to o'io inch on the aneroid baro-
meter. The following results were obtained in the
presence of experienced miners. I will, for this occasion,
call my indicator an aneroid barometer :-Aneroid baro-
meter indicated 1.50 per cent. of fire-damp; the Davy
lamp gave no indication. Aneroid barometer indicated
3'00 per cent. of fire-damp; the gas could be detected by
the Davy lamp, which gave a small pale blue flame.
Aneroid barometer indicated 8:00 per cent of fire-damp;
Aneroid barometer
the Davy lamp exploded feebly.
indicated 1000 per cent. of fire-damp; the Davy lamp
exploded fiercely. Aneroid barometer indicated 6.00 per
cent. of fire-damp; the Davy lamp did not explode, but
flame elongated greatly."

Armenian or Diamond Cement.-This article, so much esteemed for uniting pieces of broken glass, for repairing precious stones, and for cementing them to watch-cases and other ornaments, is made by soaking isinglass in water until it becomes quite soft, and then ammoniacum have been dissolved. The jewellers of Turkey, who are mostly Armenians, have a singular method of ornamenting watch-cases, &c., with diamonds and other precious stones, by simply glueing or cementing them on. The stone is set in silver or gold, and the lower part of the metal made flat, or to correspond with the part to which it is to be fixed; it is then warmed gently, and has the glue applied, which is so very strong that the parts so cemented never separate. This glue, which will strongly unite bits of glass, and even polished steel, and may be applied to a variety of useful purposes, is thus made in Turkey :-Dissolve five or six bits of gum mastic, each the size of a large pea, in as much spirits of wine as will suffice to render it liquid; and in another vessel dissolve as much isinglass, previously a little softened in water (though none of the water must be used), in French brandy or good rum, as will make a two-ounce phial of very strong glue, adding two small bits of gum albanum, or ammoniacum, which must be rubbed or ground till they are dissolved. Then mix the whole with a sufficient heat. Keep the glue in a phial closely stopped, and when it is used set the phial in boiling water. Some persons have sold a composition under the name of Armenian cement in England; but this composition is badly made; it is much too thin, and the quantity of mastic is much too small. The following are good proportions: Isinglass, soaked in water and dissolved in spirit, two ounces (thick); dissolve in this ten grains of very pale gum ammoniac (in tears), by rubbing them together; then add six large tears of gum mastic, dissolved in the least possible quantity of rectified spirits. Isinglass, dissolved in proof spirit, as above, three ounces; bottoms of mastic varnish (thick but clear), one and a-half ounces; mix well. When carefully made, this cement resists moisture and dries colourless. As usually met with, it is not only of very bad quality, but sold at exorbitant prices.-Tinman's Manual and Sci. Amer.

so. Such substances include thin india-rubber, artificially prepared graphite, unglazed earthenware, &c. The law of diffusion, as educed by Mr. Thomas Graham, F.R.S., would appear to be as follows:-A gas diffuses into another gas or into space in the inverse ratio to the square root of its density. In the application of this law to the indication of the presence of fire-damp I follow my original thought, and use india-rubber. I fill a balloon of thin india-rubber (just such a balloon as that used by children for a plaything) with atmospheric air, and I place it under a lever. If now the apparatus be carried into a mine containing fire-damp, the fire-damp diffuses into the balloon, in accordance with the above law, quicker than the atmospheric air diffuses out from the balloon, and the result is that there is an increase of volume within the balloon, and this causes expansion, just as would occur if so much air were forced into it. I cause this increase of size to move a lever, and thereby to make a galvanic circuit, and so to telegraph to a distance, while it also rings a bell on the spot. This particular arrange-mixing it with spirit in which a little gum mastic and ment is intended to give warning of a slow accumulation of fire-damp, and in practice it answers perfectly, giving at each interval of an hour the increasing amount per cent. of fire-damp present at that part of the mine. Supposing the atmosphere, then, to remain without alteration the balloon remains of the same size, consequently the alarum would ring continuously for several days, but if the mine were purified, the balloon would shrink in consequence of diffusion, and the alarum would cease. If it be desired to give instant notice to the men at work, or to the people above ground, from the working place, I use a porous battery cell, which, with a small column of mercury, gives warning in a few seconds of sudden irruption of firedamp. The action of this instrument is so immediate that, unless seen, it would appear to be incredible; it is, nevertheless, trustworthy and certain. Supposing the atmosphere which has caused the indication to remain unaltered, then the instrument empties itself by effusion, and the indicator returns to the original zero, and remains at that point until the mine is ventilated, when the indicator retires from zero, thus indicating the purification of the dangerous place. These remarks also apply to the pocket instrument described below. The instruments above spoken of are intended to give warning alone; but if it be desired for the information of viewers, inspectors, owners and others to ascertain the amount per cent. of fire-damp present in the air of mines, I vary the form of my apparatus, but the most convenient form is that which is assumed in the small aneroid barometer for the waistcoat pocket. The mercurial barometer, when fitted with the necessary accompaniments, gives very satisfactory results, as also does a column of mercury, not representing a barometer. As regards the aneroid barometer, I remove the brass back, and replace it by a piece of porous tile-the ordinary biscuit-ware of Wedgewood. In my first experiments I used a piece of a broken flower-pot, which gave as good results as could be wished for. The instrument so completed, with a few additional and purely mechanical arrangements, which I would describe were there space in this letter, may be used as an ordinary aneroid barometer, but at the time of using it, to tell the amount of fire-damp present, it is necessary to close a valve by a small screw. Then having read the point at which the barometer stands, and noting this as the zero, to remove a brass cap, which protects the porous tile; and if there be any fire-damp present the hand travels over the face of the dial, because the diffusion of the fire-damp into the chamber of the aneroid barometer causes an increased volume, which, being compelled to occupy a fixed space, causes pressure on the partly exhausted chamber within that space, and thus causes the hand to move over the face of the dial, indicating unfailingly the amount per cent. of explosive gas. In round numbers, 1 per cent. of gas is equal to or inch,

ANSWERS TO CORRESPONDENTS.

All Editorial Communications are to be addressed to the EDITOR, and Advertisements and Business Communications to the PUBLISHER, at the Office, 1, Wine Office Court, Fleet Street, London, E. C. Private

letters for the Editor must be so marked.

We have received a note from Mr. Le Neve Foster, stating that there are no more copies of Dr. Hofmann's Exhibition Report for sale.

Quero.-Should read all the lectures attentively. The term was first used by Laurent, who distinguishes two kinds of compound bodiesAplones, or simple combinations, and Diamerones, or complex or divis able combinations. See "Chemical Method" by Laurent, published by the Cavendish Society.

Books Received."A Dictionary of Chemistry, &c.," by A. Watts B.A., F.C.S.; Part XXXII., Phenylamines to Phosphorus.

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SCIENTIFIC AND

ANALYTICAL

CHEMISTRY.

Analysis of the New Phosphatic Rock Recently covered in Wales, by Dr. T. L. PHIPSON.

In which Fe and Ca are substituted one for the other in various proportions. As it contains no oxide of manganese, it may be regarded as triplite in which the manDis-ganese is replaced entirely by lime, and the name calctriplite proposed for it. The rock is mixed mechanically with pipeclay or aluminous schist (silicate of alumina) insoluble in hydrochloric acid. Some specimens contain a little carbonate of iron, and in No. IV. there is a good deal of carbonate of lime. I look upon the discovery of this new rock as likely to prove a valuable source of phosphoric acid in the arts, and trust that the dimensions of the lode are really as great as they have been represented; but I do not believe, as stated in The Reader, October 21, p. 464, that "the phosphatic mine is readily accessible and naturally drainable to a depth of about 500 miles."(!)

AN extensive deposit or lode of phosphatic material has lately been discovered in Wales, about sixteen miles from Oswestry, in the neighbourhood of Cwmgynen, by Mr. Hope Jones. Attention was called to this deposit by Professor Voeclker, in a paper read a few weeks ago to the British Association at Birmingham; but, unfortunately, the Professor gives no analysis of the rock in his otherwise interesting paper, contenting himself with reference only to the percentage of phosphate of lime yielded by certain isolated specimens.

To supply this want, I publish the following analyses of four different samples of the phosphatic rock, with the permission of Messrs. Griffin, Morris, and Griffin, the eminent agricultural chemists, of Wolverhampton, for whom the analyses were made.

The rock is massive, of a very dark olive colour, inclining to black, and yields a grey powder when pulverised. It resembles certain varieties of triplite or altered triphane. I have sought particularly in it for lithia and vanadic acid, of both of which I have found very minute quantities, scarcely worth alluding to in a practical point of view. In nature this phosphatic rock forms a wide perpendicular vein between clay-schist and pipe-clay, and in the neighbourhood of a dark bituminous limestone, which also contains a notable proportion of phosphoric acid. In the following analyses No. I. and No. II. were solid specimens, weighing several pounds, taken from different localities; No. III. was a pulverised specimen from another part of the mine, and No. IV. is a mean analysis of three other distinct specimens:

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Trialcoholic borates, whose preparation by the methods of Ebelmen and Rose is difficult, may be obtained readily, and in large quantities, by causing an excess of alcoh 1 to act on boric anhydride, in a digester at about 120°. We separate the boric ether from the unattacked alcohol by fractional distillation. On treating the different por tions with concentrated sulphuric acid two layers are obtained, the upper one containing the ether mixed with a little alcohol and a trace of sulphuric acid.

Trialcoholic borates, heated with boric anhydride, combine directly with a molecule of the latter, forming monoalcoholic borates

B

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B

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This transformation of trialcoholic ethers is complete. If, in the action of boric anhydride on alcohols, instead of an excess of alcohol, an excess of the anhydride be used, a mixture of alcohol and mono- and trialcoholic borates is obtained. In this case the alcohol and trialcoholic ether are removed by distillation, which is continued until the liquid has attained a temperature 20° or 30° above the boiling point of the trialcoholic ether. The residue consists of monoalcoholic borate, contaminated by boric acid; these are separated by means of anhydrous ether, which simply dissolves the boric ether. Alcohol will not serve for this purpose, because alcohols act energetically on monoalcoholic borates, transforming them into trialcoholic borates. By treating monoalcoholic borates by alcohols homologous to those which contributed to the formation of these borates, we prepared mixed methyl-ethylic and ethyl-amylic boric ethers. Monoalcoholic borates are dense liquids, which cannot be distilled. Submitted to a high temperature, they split

* Comptes Rendus, lxi., 697.

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On the Use of Bisulphate of Soda as a Substitute for the Bisulphate of Potash in the Decomposition of Minerals, especially the Aluminous Minerals, by J. LAWRENCE SMITH, Professor of Chem., University of Louisville.

IN referring to the more recent works on analytical chemistry, I perceive that the bisulphate of potash is still used to the almost utter exclusion of bisulphate of soda in rendering certain minerals soluble; and it is still recommended as the proper agent to fuse with aluminous minerals, as corundum, emery, &c.

This subject occupied my attention to a considerable extent when engaged in the preparation of two memoirs on the geology and mineralogy of emery presented to the French Academy of Sciences in 1850, as well as in some investigations I am now making on the emery from Chester, Mass. In the above researches I had a

large number of corundums and emeries to analyse. The powdered minerals were fused with the bisulphate of potash in the usual way, and I found no difficulty in decomposing the minerals; but unfortunately during the operation a double salt of potash and alumina is formed which is almost insoluble in water or in the acids; and it is only by a solution of potash that it is first decomposed and afterwards redissolved. There are many disadvantages and delays attendant upon this method, which experience soon exhibits-as the constant deposition of alum if the solution is not kept quite dilute. I therefore experimented with the bisulphate of soda, knowing that the double salt of alumina and soda was quite soluble, and my results were everything that could be desired; for while the soda salt gives a decomposition at least as complete as the potash salt, the melted mass very soluble in water, and in the future operations of the analyses there is no embarrassment from a deposit of alum. The manner of employing the bisulphate of soda in the analysis of emery will be referred to in a future article on the emery of Chester, Mass.

is

Preparation of the Bisulphate of Soda.-The ordinary commercial article is not sufficiently pure for use, and I prepare it from pure carbonate of soda or sulphate of soda that has been purified by recrystallisa

• See American Journal of Arts and Sciences, vol. x., 1850, and vol. xi., 1851.

tion. In either instance pure sulphuric acid is added in excess to the salt in a large platinum capsule, and heated over a flame until the melted mass, when taken up on the end of a glass rod, solidifies quite firmly. The mass is then allowed to cool; moving it over the sides of the capsule will facilitate this operation. When cool it is readily detached from the capsule, is then broken up and put into a glass stoppered bottle. So far as my experience has yet gone, in almost every instance where we have been in the habit of using bisulphate of potash the bisulphate of soda can be substituted.-American Journal of Science and Arts.

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I supposed that by submitting isatine to the action of a more energetic reducer, such as a solution of hydriodic acid, at above 100°, the reduction would be more complete and the indigotine regenerated.

This did not happen, but some reactions took place at from 130° to 140°, which furnished the new compounds forming the subject of this memoir.

I heated pure isatine at 140° in a closed vessel with a solution of hydriodic acid of 45° Baumé. A large quantity of iodine separated itself, with the formation first of isathyde, then of a dark green amorphous mass,

insoluble in water.

This product, washed with sulphurous acid to eliminate all the iodine, and then in pure water, is a mixture of three new bodies capable of being separated by alcohol and ether. Boiling alcohol removes a slightly soluble white substance; then a violet-red matter almost insoluble, and which can be completely dissolved only by repeated exhaustion.

insoluble in all neutral solvents. The alcoholic solutions, There remains a considerable residue of a green matter, dried precipitate yields a red body to ether, while the being concentrated, may be precipitated by water. The white body refuses to dissolve in this menstruum. alcohol or in concentrated acetic acid, when it is deposited The white matter may be purified by crystallisation in in the form of microscopic needles.

liquid may be freed from the small quantity of the white The red matter obtained by evaporating the etherial body accompanying it by washing it in hot caustic soda and then dissolving in crystallisable and boiling acetic acid. On cooling it separates in the form of fine dark

red needles.

The latter body is allied to indine, which M. Laurent isathyde, but is distinguished from it by its composition obtained by the action of caustic soda on sulphuretted and by certain differences in its properties.

determined by the following analyses:— The composition of these three new derivatives was

↑ Comptes Rendus, lxi. 284.

NEWS

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Carbon

Hydrogen

Theory.

74'41 5'42

4'37

Both the red and the green matter fix hydrogen under the influence of alkaline reducers, and change into white or yellow bodies, capable of reproducing by oxidation the primitive compounds.

For these bodies I propose the following names :—
1. Green matter, isatochlorine.
2. Red matter, isatopurpurine.
3. White matter, isatone.

They have some analogy with the products prepared by M. Laurent by treating sulphuretted isathyde with soda, but are easily distinguished from them. The results obtained by analysis are very different, and the characteristics do not agree on many points.

TECHNICAL CHEMISTRY.

The Past and Present History of Alum, by J. CARTER BELL, Esq., F.C.S., Associate of the Royal School of Mines, London.

IN reviewing the various departments of manufacturing chemistry we are sensibly struck by the great improvements made in the different branches within the last few years, and the great advantages which have accrued from them; for in many instances the price of the chemical products has been reduced to one-half and even one-fourth what it originally was, owing greatly to the large amount of skill which is brought to bear upon the subjects in question. The past and present history of alum offers a very good example of the strides which manufacturing chemistry has made. The discovery or invention of alum seems to be quite lost; where it was first made or discovered is difficult to say, for the ancients seem to have confounded many salts under the name of alum. At he present day the word alum is applied to a number of double salts, such as the iron, chrome, soda, potash, and ammonia alums.

Though all these may be composed of different elements, yet they are arranged in the same manner, and may be expressed by a general formula

MORO3+ M2033RO3 + 24aq.

The alums spoken of here refer to the ammonia and the potash salts. What the Romans called "alumen” was only the green sulphate of iron. But alum must have been very early known, for Herodotus, who lived 460 years before the Christian era, mentions Egyptian alum, and says that the King of Egypt sent a thousand talents to the people of Delphos on the destruction of their temple by fire; but, according to Beckmann, the Greeks and the Romans speak of nothing but natural alum; and several of our most acute mineralogists (mentioning Scopoli and Sage) deny the existence of native alum. There must be some mistake on this point, for several alums are found native. In the first place, there is the potash alum, found in the Lipari Islands, Sicily, St. Michael, Norway, and even in Yorkshire. The soda alum is found in the Neapolitan Solfatara, Island of Milo, and Mardoza. The ammonia alum at Thuringia, Bohemia. If all these alums are found now, there is no reason to suppose they were not found then; on the other hand, there is every reason to suppose they were acquainted with alum and its uses; for if we look at the skill they possessed in the art of dying, such as their Tyrian purple, etc., one can readily believe that alum was well known to them, and that they found it in its natural state; for even Pliny seems to have been acquainted with it, for he says one kind was white, and used for dyeing wools of a bright colour. In Pliny's time the Egyptian alum was considered the best, and, according to Beckmann, it still forms one of the exports of Egypt; "but," he says, "I am acquainted with no author who mentions the place where it is found or made, and as the smallest trace of alum works is not to be found amongst the ancients, the only conclusion is that they must have found the natural alum or some other salt to which they gave that name.”

We now come to the history of our present alum. It was first made in the East. Beckmann says the invention is later than the twelfth century; but this cannot be correct, for Geber, the Arab physician, who lived about the eighth century, mentions it, and describes the method of making burnt alum. It seems that the Italians procured their alum from the Levant; but when these countries were in possession of the Turks, the people who denominated themselves Christians did not like purchasing of the infidels, and in the course of time they learned to make their own alum: then the chief manufactory of this important salt belonged to the Papal States, and the works which are near Civita Vecchia are considered by some to have been the first of any importance. The founder of them was John di Castro. He acquainted Pope Pius II. of the place where the aluminous material might be found. These works succeeding beyond their expectations, the Pope thought Castro worthy of high honours, and a statue was erected to him in his own country, with this inscription-"To John di Castro, the inventor of alum." When the alum works of the Papal States were found to be successful, others were erected in various parts of the Continent, The first works which were erected in England were at Gis borough, in Yorkshire, in the reign of Queen Elizabeth. The manufactory belonged to Sir Thomas Chaloner. He was obliged to engage privately some of the Pope's workmen, as there was nobody who understood the process in this country. But when the Pope heard of this, he

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