ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 461 



(2) Eye-pieces and Objectives- 



Hart-wig, H. — Zur Berechnung dreitheiliger Fernrohr- und Mikroskopobjective. 

 (On the Calculation of Three-lensed Telescope and Microscope Objectives.) 



Zeitschr. f. Instrumentenk., XX. (1900) p. 230. 



Stbehl, K. — Studien an Mikroskopobjectiven. (Studies on Microscope Objectives.) 



[The author makes a series of comparisons on the combinations of objectives 



and oculars from two firms whom he calls X and Y. Elaborate tables 



of results are given.] Zeitschr. f. wiss. Mikr., XVII. (1900) pp. 425-32. 



(4) Photomicrography. 



A First Book of the Lens. — C. Welborne Piper's book * with the 

 above title is intended to be an elementary treatise on the action and use 

 of the photographic lens. Its title accurately expresses the scope of the 

 work, and the various diagrams are very clear and instructive. The 

 subject of lens combination is very fully illustrated. The topics of the 

 ten chapters are : — Light and optics ; action of lenses ; focal points and 

 distances ; combining lenses ; aberration ; scale ; intensity and illumina- 

 tion ; depth ; focussing scales ; measuring lenses ; types of lenses. There 

 is also an appendix of tables. 



Lantern-Slide Making.f — Number 22 of the " Amateur Photo- 

 grapher " library consists of a handy little volume, by the Eev. F. C. 

 Lambert, M.A., under the above title. The book, which seems very 

 clearly and concisely written, is expressly intended to be a guide to 

 those who are as yet quite ignorant of the subject. At the same time 

 it is hoped that the experienced worker may here and there pick up a 

 useful stray bint. The work is divided into twenty chapters, with an 

 appendix. 



Chbtney, J. S. — Photomicrography. Micr. Bull., 1900, p. 17. 



(5) Microscopical Optics and Manipulation. 



Stbehl, K. — Theorie der allgemeinen Mikroskopischen Abbildung. (Theory of 

 the Microscopical Image.) Erlangen (Blaesing), 1900, 8vo, 38 pp. 



(6) Miscellaneous. 



Launois, P. E. — Les Origines du Microscope. Leeuwenhoek, sa vie, son oeuvre. 



Comptes Bendus de I Assoc. Francaise, Sess. 28, pt. 1, p. 82. 



B. Technique. t 



(1) Collecting- Objects, including- Culture Processes. 



New Incubator.§ — Dr. N. Gertler has patented an ingenious form 

 of thermostat which is specially suited for medical men (fig. 97). The 

 case is double, and is made of wood, the interspace being filled with felt 

 or with infusorial earth. The heater or thermophore is brick-shaped, 

 and is placed on the floor of the apparatus. It is made of metal, is 



* Hazell, "Watson, and Viney, 170 pp. and 67 figs. | 



t Hazell, Watson, and Viney, 144 pp. and 27 rigs. 



% This subdivision contains (1) Collecting Objects, including Culture Pro- 

 cesses ; (2) Preparing Objects ; (3) Cutting, including Imbedding and Microtomes ; 

 (4) Staining and Injecting ; (5) Mounting, including slides, preservative fluids, &c. ; 

 (6) Miscellaneous. 



§ Centralbl. Bakt, l t6 Abt., xxix. (1901) pp. 668-72 (1 fig.). 



