20 



THE AMERICAN MONTHLY 



[January, 



cussed at considerable length. Dr. Cur- 

 tis stated that since the appearance of 

 Klein's Atlas, he had devoted some time 

 to the investigation of these statements ; 

 that, with high powers, and the object just 

 out of focus, he had seen an appearance 

 something like that illustrated by Klein, 

 and described by Fleming as an " intra- 

 nuclear net-work." When the corpuscle 

 is in true focus its surface presents a 

 granular appearance, of a somewhat regu- 

 lar pattern, like the surface of a rasp- 

 berry. 



The meeting closed with an exhibition 

 of interesting objects. 



GRIFFITH CLUB, MICH. 



The Griffith Club of Microscopy, of 

 Detroit, Mich., is a new organization 

 which we are glad to hear from. We 

 have a report of a paper read at its second 

 monthly meeting by Mr. J. C. Holmes. 

 The paper was on " The Progress and 

 Uses of the Microscope", and is not 

 readily summed up. 



Mr. Holmes' paper was listened to with 

 the closest attention and was highly com- 

 mended by his associates. At its close 

 Prof. E. W. Wetmore, President of the 

 Club, presented the following formula for 

 determining the magnifying power of a 

 microscope : 



1. Divide ten inches by the nominal 

 focal length of the objective ; this will 

 give the magnifying power of the glass. 



2. Divide ten inches by the linear dis- 

 tance between the centers of the field- 

 glass and the eye-glass of the eye-piece. 



3. Multiply these quotients together and 

 you will get a close approximation to the 

 working power of the combination, when 

 used with the standard length (ten inches) 

 of tube. 



To put the above in mathematical form, 

 let F O equal the nominal power of the 

 object-glass : let F I equal the distance be- 

 tween the lenses of the eye-piece; then 100 

 divided by F O multiplied by F I, equals 

 the magnifying power of the instrument. 

 For an instrument with a longer tube, 

 substitute the length of the tube for the 

 first ten inches in the formula. 



After the annomicement that Dr. 

 Main, of Jackson, Mich., would, , St the 

 next meeting of the Club, read a paper on 

 his specialty, " Section Cutting," the for- 

 mal session ended. 



SAN FRANCJf^CO. /^ 



We are obliged to.-iOmit ffom this issue 

 a report of the San Francisco S^iefy. 



Reviews of Books. 



The Microscopist. — A Manual of Micros- 

 copy and Compendium of the Micros- 

 copic Sciences, Micro-Mineralogy, 

 Micro-Chemistry, Biology, Histology, 

 and Pathological Histology. By J. H. 

 Wythe, A. M., M. D. Third edition, 

 with 205 illustrations. Philadelphia : 

 Lindsay and Blakiston. (8vo. Price, 

 $4.50.) 



This is a book of 250 pages, printed on 

 good paper with clear type, and replete 

 with excellent illustrations. It is so well 

 known to microscopists, however, that we 

 need not enter into a detailed review of 

 its contents. There are some portions 

 that should be rewritten to bring them up 

 to date, particularly those which relate to 

 the capabilities of modern objectives ; but 

 in speaking of this we may also add that 

 there is not one single published work, 

 treating of the microscope, which em- 

 bodies the results of recent investigations 

 upon the theory of the microscope, the 

 proper methods of illumination, and va- 

 rious other subjects of theoretical and 

 practical importance. Most of the illus- 

 trations are printed in one or more colors, 

 on full-page plates, thus greatly adding 

 to the good appearance of the book. 



The field covered is a large one, em- 

 bracing all the subjects mentioned in the 

 title, and many others. The work con- 

 tains much that is not usually found in 

 books of a similar character e. g., the 

 micro-chemical tests, and some tables 

 giving the classification of certain anifnals 

 and plants. 



We believe it is a valuable work for the 

 general student. 



Exchanges. 



[Exchanges are inserted in this column without 

 charge.] 

 Polyzoa, Palates of Mollusca, Foraminifera, Sponge 

 and Holothurian-Smcules, Synapta-Anchors, Chirod- 

 ota-Wheels, EchinjjB-Spines, Minute Sea Shells, in ex- 

 change for Polyzoa; Foraminifera, Histological and 

 Pathological preparations, etc. Also, a quantity of 

 Sea Shells in exchange for Land and Fresh-Water 

 Shells. 



F. M. HAMLIN, M. D., 



Auburn, N. Y. 



J. 'J. B. Hatfield. Arsenal Avenue, Indianapolis, 

 Indiarta, will exchange Bleached Plant-Sections for 

 good Diatomaceous, (material. List furnished on ap- 

 plication, c 



For fine specimens of Tingis hyalina, send a 

 stamped envelope to 



ALLEN Y. MOORE, 

 / • j?6 Dodge St., Cleveland, Ohio. 



