26 



SCIENCE. 



CORRESPONDENCE. 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No notice is taken of anonymous communi- 

 cations.] 



Cumberland University, ) 

 Lebanon, Term., Jan. 23, 1882. \ 

 To the Editor of " SCIENCE." 



Dear Sir — When experimenting with the so-called 

 nitrogen iodine a short time ago, I met with an accident 

 which might have been very serious. I had prepared 

 about a grain of this compound by the action of am- 

 monia upon iodine, and it had stood over night in a 

 watch-glass with a slight excess of ammonia. I pro- 

 ceeded to wash it with water preparatory to drying it for 

 use in the lecture-room. Wheu washing it through the 

 third water and stirring it lightly with a glass-rod to make 

 the cleansing more thorough, a violent explosion took 

 place, filling my face and eyes, I washed them as quickly 

 as I could with water and dilute alcohol, and there fol- 

 lowed only a slight inflammation of the conjunctiva, 

 which subsided in a few days. 



I have repeated the experiment several times, and in 

 every case have found that when the compound stands 

 in an open vessel for twelve hour's under ammonia, 

 it contains a compound which is explosive under water 

 upon slight causes. What this compound is I have not 

 ascertained. At the same time the greater part of sub- 

 stance remains undecomposed and is merely scattered 

 about by the explosion. This when dry presents the phe- 

 nomena of the ordinary iodine. The subject deserves 

 further investigation, 



Very truly yours, 



J. I. D. Hinds, 



BOOKS RECEIVED. 



The Brain of the Cat (Felis domestica), a Prelimi- 

 nary Account of the Gross Anatomy, with four plates, 

 by Burt G. Wilder, M. D., Professor of Compar- 

 ative Anatomy, &c, in Cornell University, &c, &c. 



This is a reprint from the proceedings of the American 

 Philosophical Society, July 15th, 1881, and is the first of 

 a series of contributions to the knowledge of the brain 

 of the domestic cat. The present paper is divided into 

 four parts, the second of which is a continuation of the 

 paper by Professor Wilder on " A Partial Revision of 

 Anatomical Nomenclature with especial reference to that 

 of the Brain," published in Science on the 19th and 29th 

 of March, 1881. Part III. relates to a number of points 

 suggested for study, in which a knowledge of the cat's 

 brain is not sufficiently understood. The four plates are 

 very elaborate and well executed, and describe with 

 great minuteness all that can be seen by natural vision of 

 the cat's brain, both externally and in section. These 

 valuable papers by Professor Wilder promise to mark an 

 epoch in the literature of this subject. 



The Thirty-sixth Annual Report of the Director 

 of the Astronomical Observatory of Ilaivard Col- 

 lege, by Edward C. Pickering. Cambridge, 

 1882. 



An abstract of the report will be prepared for 

 " Science." The report is a cheering one, speaking of 

 the enlarged resources of the Observatory, the increased 

 number of assistants, and efficient work of all engaged 

 in making observations or their reduction. 



The Formation of Vegetable Mould through 

 the action OF Worms, with Observations on their 

 Habits, by Charles Darwin, LL.D., F.R.S., with 

 illustrations. M essrs. D. Appleton & Conipsny. 

 New York. 1882. 



As this interesting work will be reviewed in this jour- 

 nal the simple announcement of its publication will suf- 

 fice. 



Studies in Astronomy, by Arthur K. Bartlett, 

 M. D. 2nd edition, revised and rewritten. Pub- 

 lished by the author. Battle Creek, Michigan. 35 

 cents. 



As an introduction to the science of Astronomy, this 

 little book presents many advantages, the subject is well 

 handled and presented in a very attractive form. 



Bulletin No. i of the American Museum of Natural 

 History, December 23, 1881. Three articles by 

 Professor R. P. Whitfield, illustrated. 

 This publication has been produced in a form worthy 

 of the establishment that issued it. It proposes to be one 

 of the most valuable bulletins published by scientific in- 

 stitutions. 



Bureau of Education. Circulars of Information, 

 No. 4, 1881 ; Washington, 1881. 

 This is an exhaustive description of the work of educa- 

 tion in France. 



Proceedings of the American Society of Micro- 

 SCOPISts. Fourth Annual Meeting held at Colum- 

 bus, Oh : o. August, 1 88 1. 

 This publication, which does credit to the publication 



committee, contains several valuable papers with seven 



pages of illustrations, and will be noticed at greater 



length on another occasion. 



How to See with the Microscope, by J. Edwards 

 Smith, M. D. ; Duncan Brothers, Chicago. 

 This book has been severely handled by some critics, but 

 in our opinion it contains more original writing than any 

 book on the subject issued during the last two years, and, 

 coming from the hands of a thorough expert micro- 

 scopist, merits attention from all using the instrument. 

 The work would be useless to a beginner, who should 

 use Professor J. Phin's excellent little manual, but to one 

 who has made some progress with the instrument Pro- 

 fessor Smith's work will prove quite useful. 



LUMINOUS INTENSITY OF THE VOLTAIC 

 ARC. 



M. Niaudet, in his excellent work, les Machines c'lec- 

 iriques h courants continus, gives quite an exhaustive 

 treatise on the voltaic arc ; he particularly dwells upon the 

 arc obtained by a continuous current, the positive pole 

 above, and the negative below and on the same vertical 

 line. It is to this case that the following extract has ref- 

 erence : 



" Relative luminous intensity of the carbons. — It is 

 very easy to see that the light directed against the lower 

 pole is very much greater than that carried against the 

 top. To see this, it is only necessary to place the two 

 hands, the one above and the other below the arc, and to 

 observe them. The difference is striking. 



M. Fontaine has taken a series of photometric measures 

 in a vertical plane, and in all planes varying from the hori- 

 zontal to the vertical above and below the horizontal 

 plane passing through the arc. 



These experiments have proved that the intensity is 

 maximum between 45 and 60° below the horizontal plane, 

 and that it is about ten times greater than the intensity 

 measured at 45 above the horizontal plane. In the 

 same investigation, M. Fontaine has compared the lumin- 

 ous intensities of the voltaic arc furnished by a machine 

 with alternate currents, with those we are now discussing. 

 The same mechanical work was employed in the produc- 

 tion of both arcs ; the intensity was the same in the hori- 

 zontal plane ; but the mean intensity was much less. 



According to M.Fontaine, the mean intensity of the 

 light given by the first arc is three limes that given by the 

 second." 



