i6o 



THE AMERICAN MONTHLY [August, 1883. 



Simply a false notion of angle of aper- 

 ture. The American list implies that an 

 angle of 40° makes a first-rate glass of 

 the i-inch, and a third rate of the -|-inch, 

 whereas, the facts in the case are, that 

 an angle of 40*^ is the same thing in the 

 one glass as ia the other, and will do as 

 good work. 



True, the American list offers glasses 

 lower than the German, but the list tells 

 us, they are third rate, and we don't want 

 third-rate glasses. The American list is 

 a slap in the face of both student and pro- 

 fessor, and a compliment to the man who 

 is in microscopy what the owner of a 

 |;2ooo racer is in social economy, be that 

 much or little. The list implies that first- 

 class objectives are neither for professor 

 or student, by tacking their titles on to 

 second and third rate lists. Now, it may 

 be after all, the " professional" and " stu- 

 dents " glasses are first-rate in correc- 

 tions ; but the maker knows better than 

 I ; and while he calls them second and 

 third rate, I must take him at his word ; 

 and 1 would say to him, if these glasses 

 are second and third rate, do make us 

 some first rate glasses of moderate aper- 

 ture as low as the Germans make them ; 

 if these are first-rate, say so. 



C. Onderdonk. 



Rugby, Tenn., June 11, 1883. 



MICROSCOPICAL SOCIETIES. 



At a meeting of the Royal Microscopi- 

 cal Society held in June last, a specimen 

 of rock fromSoutherlandshire was shown 

 which was said to contain the first 

 Eozoon remains that have been dis- 

 covered in Great Britain. The President 

 remarked that the specimens he had ex- 

 amined did not carry conviction of their 

 eozoon nature, but owing to the fact that 

 the rock is not in its primitive condition 

 but has been infiltrated with mineral solu- 

 tions which have replaced each other per- 

 haps several times, it is difficult to decide 

 upon the nature of the structure observed. 



NOTICES OF BOOKS. 



Normal Condition of Cellular Structure^ 

 and Peach Yellows. By D. V. Pen- 

 hallow, B. S., Botanist and Chemist 

 of Houghton Farm, iVIountainville, 

 N. Y. Diseases of plants. Series III. 



Nos. I and 2. With four colored litho- 

 graph Plates. Pamphlet, large Svo. 

 pp. 45. 



The present pamphlet is one of a se- 

 ries published by the Houghton Farm, 

 detailing the results of long-continued 

 experiments to determine the relative 

 condition of the cells of plants in health 

 and disease. The first part is devoted to 

 " The normal condition of vegetable 

 structure, with reference to cell contents." 

 Experiments were made with trees of 

 widely different relationship, growing in 

 different localities, and under conditions 

 of cultivation, as well as in the wild state, 

 and also at different seasons of the year. 

 Twenty-two different trees were se- 

 lected and three hundred and sixty exam- 

 inations made. The results are given 

 concisely and are worthy of careful study. 

 Part 2 is devoted to an investigation of 

 Peach Yellows. Tofurther this investiga- 

 tion I i;o circular letters containing printed 

 questions were sent to promment growers, 

 and it is surprising to find that only four 

 answers were received. The examina- 

 tions were carried on for an extended 

 period, both chemically and microscopi- 

 cally, and very satisfactory methods for 

 the treatment of the disease seem to have 

 been arrived at. 



The work also contains very conven- 

 ient tables of comparative measures 

 ( metres and feet ) on temperature ( Cent, 

 and Fahr.) 



Exchanges. 



For Exchxnge. — Slides of pollen of pitch pine, 

 Finns rigida, with the connection stained, for any 

 named slides of algs. Dr. C. F. Millspaugh, E. M. 

 S., Binghampton, N. Y. 



Wanted. — Trichina Spiralis, Pleurosigma Ang., or 

 other well-mounted slides in exchange for fine slides. 

 Insects, Acan, Spermatozoa of Horse, Physiological 

 and Patholoijical preparations. J. O. Stillson, M. D., 

 504 Upper Second Street, Evansville, Ind. 



For Exchange. — Well-mounted double-stained vege- 

 table preparations, also, a few first-class injected prepar- 

 ations for other well-mounted slides. N. A. Richards, 

 St. Louis, Mich. 



Well-mounted slides of Polycystina, transparent and 

 opaque, for any well-mounted slide. P. C Cole, M.D., 

 254 West F'orty-second Street, New York, N. Y. 



Wanted. — Slides of Bacteria in exchange for other 

 slides, or for cash. J. M. Adams, Watertown, N. Y. 



I 



