Apkil 6, 1883.] 



SCIENCE. 



253 



position, and that, indeed, of phytopaleontol- 

 ogy, that Saporta has prepai'ed a really noble 

 volume. He first examines the conditions of 

 the vegetable remains, their mode of preserva- 

 tion, the evidence of their vegetable natnre 

 compared with the impressions produced by 

 animals or mechanical agency. On this sub- 

 ject he adds a note of Dr. Marion, who has 

 followed the same line of research as Nathorst, 

 in carefully studying the character of the cells 

 produced hy animal agency, and who points 

 out the great difference between these tracks 

 and vegetable impressions. The second part 

 of Saporta's memoir contains a detailed exam- 

 ination of some tj'pes of fossil Algae. The 

 species described are represented, as well as 

 their living related types, with admirable care 

 and precision. Some of the documents from 

 which Saporta has derived valuable assistance 

 are from tlie works or communications of 

 American authors ; Harlania Hallii, among 

 others, is beautifully figured. With few ex- 

 ceptions, all the evidence adduced in the 

 admirable work of Saporta is opposed to the 

 opinions of Nathorst, and renders great ser- 

 vice to phytopaleontology. 



BOLTON'S QUANTITATIVE ANALYSIS. 



The student's guide in quantitative analysis, intended 

 as an aid to the study of Fresenius' system. By 

 H. Carrington Bolton, Ph.D., Trinity col- 

 lege, Hartford, Conn. New York, John Wiley 

 ^ Sons, 1882. 6 + 124 p. 8°. 



The above title is somewhat misleading ; for 

 the book, as stated in tire preface, is a series of 

 notes on a system ^of quantitative analj'sis, as 

 developed and modified bj' the author, from a 

 course of instruction originall^^ organized in 

 the School of mines, Columbia college, by Prof. 

 C. F. Chandler. Viewing the book in this light, 

 two things must be taken into consideration, — • 



first, whether the analyses given are typical 

 ones, such as would enable the student, on 

 the completion of the course, to work out bj- 

 himself the common problems of quantitative 

 analytical chemistry ; second, whether the notes 

 given under the various determinations are 

 such as explain, not only the different steps of 

 the process, but also the reasons that neces- 

 sitate them. The first of these two questions 

 we can answer decidedly in the affirmative. 

 The only criticism, that we might make is, that 

 possibly too much attention has been paid to 

 alloj's, and not quite enough to complex min- 

 eral determinations. The first analysis given 

 is baric chloride, then magnesic sulphate, and 

 other simple salts where no process of separa- 

 tion is necessary-. The book then takes up, 

 in well-chosen order, almost all the common 

 alloys and minerals, gives the simpler prob- 

 lems of volumetric work, the determination 

 of carbon, hydrogen, and nitrogen in organic 

 compounds, and many of the most striking 

 commercial tests ; such as the examination of 

 sugar, milk, mineral-water, coal, and petro- 

 leum. The notes, however, under these different 

 analyses, we cannot consider as perfectly sat- 

 isfactory. Tliey consist of a short account of 

 the process, with references to Fresenius or 

 the original article, and sometimes a tabulated 

 plan ; but no explanation of the various steps 

 is given. If, after each analysis, the reasons 

 why the different reagents had been added, 

 and otlier numerous details, had been explained, 

 the value of the book would have been much 

 greater ; for it is the want of such elucidations 

 in Fresenius that makes his system seem con- 

 fused and difficult to the young student. As a 

 whole, however, when studied, as intended by 

 the author, in connection with Johnson's trans- 

 lation of Fresenius, or when supplemented by a 

 thorough series of lectures, we can recommend 

 the book as giving a valuable course in quan- 

 titative work. 



WEEKLY SUMMARY OF THE PROGRESS OF SCIENCE. 



ASTRONOMY. 



Encke's comet, and a resisting medium in 

 space. — Dr. O. Backlund, in a paper entitled 

 Kurzer bericht ueber meine untersuchungenueber die 

 hypothese eines wiederstehenden mittels {Melanges 

 math, et astron., vi.), makes the following statement 

 of the results of his researches on Encke's comet: 

 " The investigations hitherto made of the theory of 

 Encke's comet really prove nothing as to the exist- 

 ence of a resisting medium in space. Even if we 



should succeed hy such a hypothesis to explain suffi- 

 ciently the increase of the mean motion and the 

 decrease of the eccentricity during the period 1819- 

 48, a simple hypothesis like this will not at the same 

 time suffice for the motion of the comet after 1865, 

 as the variation of the mean motion after that time 

 has most probably become different. Not until the 

 period 1865-81, and its connection with the earlier 

 one, have been fully discussed, will ifperhaps become 

 possible to find indications of the nature of the 

 unknown forces which act on the comet." — (Coper- 

 nicus, Feb. ) D. p. T. [531 



