February 9, 1883. 



SCIENCE. 



17 



far out of the way, we have the intensity of the light 

 from the sun's disc in the two instances, 2il x 64,- 

 700 = 257,000, and 326,000 instead of 53,000, times 

 that of the candle. 



In our author's observation the altitude of the sim 

 could not have been far from 12°; which, together 

 with the greater clearness of the American sliies, 

 may have produced the large discrepancies in our re- 

 sults. But assuming my results to be correct, even 

 at an altitude of 40° the sun gives out 33 times the 

 light of a Swan lamp for the same amount of power 

 expended. — w. ii. p. [9 



G-reeu fog. — A possible explanation of this diffi- 

 culty is offered by Mr. E. Dunmore, who thinks it is 

 due to the action on carbolic acid by ammonia, con- 

 verting it into aniline. Both substances are generally 

 present in an emulsion prepared with ammonia; and, 

 with regard to an acid-boiled emulsion, the gelatine 

 may of itself contain them, — the ammonia from 

 incipient decomposition, and the carbolic acid from 

 what has been used to preserve it from putrefaction 

 during manufacture. — (Brit. joum. phot., Dec. 1, 

 1882. r "(v. H. p. [10 



Cold emulsificatiou. — Mr. A. F. Genlain de- 

 scribes his method of carrying out Mr. Henderson's 

 formula for cold emulsification. He thinks that by 

 discarding the carbonate of ammonia, as Mr. Hen- 

 derson has since suggested, this will prove one of the 

 most certain processes yet discovered. — (Brit. joum. 

 p/iot, Dec. 15. 1S82.) w. ii. p. . [11 



A modified gelatine emulsion. — Mr. W. K. 

 Burton employs a process by which, in the results 

 obtained, the density of the negative will increase 

 nearly proportionally to the amount of light received. 

 By the ammonia process the density increases too 

 rapidly at first, while in the long boiled emulsion the 

 increase is too slow. But the great advantage which 

 he claims lies in the fact that the gelatine which has 

 gone through the ordeal of the operation necessary 

 to obtain sensitiveness is eliminated. It is this gela- 

 tine which he thinks gives rise to many of the evil 

 phenomena which gelatine plates exhibit, especially 

 when ammonia is used. — (Brit. joum. phot.. Dec. 1."), 

 1882.) w. II. p. [12 



CHEMISTEY. 

 {Ofini'rnI, plty^iial, and inorgank.) 



Lecture experiments. — Dr. A. W. Hoffmann 

 has devised a series of lecture experiments similar in 

 principle to those described in his Einleitung in die 

 moderne chemie. The electrolysis and formation of 

 hydrochloric acid are illustrated in a simple manner, 

 and several improvements are introduced into experi- 

 ments illustrating tlie phenomena of combustion. 

 Some experiments on the volumetric relations of 

 gases are suggested, and the analysis of ammonia 

 gas is made less tedious in its details. A new form 

 of apparatus is described, which is intended to give 

 an experimental illustration of the law of Dulong 

 and Petit. — (Berichte deutsck. chem. rjeselhch., xv. 

 2656.) c. F. M. [13 



Lecture experiments ■with zinc-dust and sul- 

 phur. — In the experiment which is usually per- 

 formed to illustrate chemical combination, instead of 

 heating sulphur with copper or iron filings, Schwarz 

 makes an intimate mixture of sulphur and zinc-dust, 

 and ignites it with a match. It burns like gun- 

 powder, with a bright greenish flame, leaving a resi- 

 due of zinc sulpliide. When heated in a retort with 

 carbonic disulphide, zinc-dust is converted into the 

 sulphide, and carbon separates in the form of soot. 

 Many complex organic compounds containing sul- 



phur are decomposed when heated with zinc-dust 

 with the formation of zinc sulphide and carbon com- 

 pounds of a simpler order. — {Berichte deutsch. chem. 

 gesellsch., xv. 2.505.) c. F. M. [14 



Preparation of oxygen at ordinary tempera- 

 tures. — When potassium permanganate is mixed 

 with concentrated nitric acid, M. Guyard finds that 

 oxygen is liberated from the permanganic acid with 

 great regularity, and the action continues until two 

 and a half equivalents are set free. If the apparatus 

 is then immersed in boiling water, the disengagement 

 of gas is kept uj) until altogether thi'ee equivalents 

 of oxygen are obtained from the permanganic acid. 



— (BuH. soc. c/(eH/., xxxviii. 383. ) c. F. M. [15 

 The double haloid salts of mercury. — For 



the purpose of obtaining a more definite knowledge 

 of reactions which take place in the formation of 

 double salts, M. Berthelot has determined the heat 

 of formation of certain double salts of mercury. It 

 appears that the quantity of heat liberated in the 

 foi'mation of the anhydrous salt is smaller than when 

 the hydrous salt is formed: Hg CI.,. K CI = + l""'- 9; 

 Hg CL,. K CI. H.,0 = -f 2="'- 7. The acid salt Hg I. 

 2 II I. sets fi-ee the same amount of heat as the salt 

 Hg 1. 2 K I. While the heat of formation of the 

 three haloid salts of potassium is nearly the same, 

 it is very different in the corresponding salts of 

 mercury : Hg Cl^ = 11""- ; Hg Br._, = 15«"'-4; Hg I,, = 

 21"''-7. This inequality, as the author proposes to 

 show, is the determining cause of double decomposi- 

 tions. — {Bull. soc. chim., xxxviii. 300.) c. F. M. [16 



METALLURGY. 

 NeMV process of manufacturing aluminum. — 



A mixture of alum and i)itch is calcined, retorted, 

 and leached. The residue contains 84 per cent of 

 alumina, while the old process yielded only 65 per 

 cent. The alumina is then made into the chloride; 

 and the chloride is treated with sodium, in the usual 

 way, to obtain the metal. The process has been in- 

 vented by Mr. James Webster of Holywood, England. 



— (Eur/, jjuji. JoMrii., Dec. 23, 1882.) K. H. K. [17 

 Fine gold from chlorination. — Gold produced 



from the mines of the Canada consolidated gold min- 

 ing company by Mear's chlorination process is reported 

 to be the finest ever received by the U. S. mint. — 

 {Eny. min. joum., 'Nov. 18, 1SS2.) B. H. p.. [18 



Lnprovements at Batopilas in silver amal- 

 gamation. — The losses of 50 oz. per ton in the tails 

 by the old arrastras have been reduced to 8 oz. per 

 ton. The improvements consist of pan amalgamation 

 for the first and second class ore, concentration fol- 

 lowed by pan amalgamation for third-class ore. The 

 loss in mercury has been j-educed at the same time 

 from 27 per cent, as incurred by the arrastra, to 2| 

 per cent with the pan. — (Enq. iidn.journ., Nov. 18, 

 1882. ) p.. H. u. [19 



GEOLOGY. 

 Lithology. 



Some Himalayan melaphyrs. — Col. C. A. Mc- 

 Mahon has made a microscopic examination of certain 

 traps regarding wliose origin some doubt had been 

 expressed. The prevailing tendency had been to 

 hold that they were sedimentary rocks metamor- 

 phosed ; but McMahon holds that his microscopic re- 

 searches afford abundant proof that they are altei-ed 

 basaltic lavas. Two plates accompany the paper, 

 which indicate either a very low grade of art or 

 a very small appropriation. — (Bee. geol. surv. India, 

 1882, XV. 155. ) M. E. -vv. [20 



Rocks classified by formations. — Prof. E. 

 Eenevier has published the following classification. 



