554 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



through the tube and are again reflected at the hypotenuse of an isosceles 

 right-angled prism. The emergent rays can then be received on any 

 convenient screen. 



Koristka's Abbe Camera Lucida with Lens-Holder.* — This instru- 

 ment, shown in fig. 136, while principally designed for low powers, is also 

 adapted for drawing objects their natural size without the aid of a lens. 

 The camera lucida with its large mirror, 90 by 150 mm., and with 



Fig. 136. 



gilded double prism, takes a very large field. It is fitted with two series 

 of smoked glasses, one for interposing between the prism and the mirror 

 and the other for insertion between the prism and the magnifying lens. 



(6) Miscellaneous. 



Jena Glass.f — The nature of the contents of this book place it out 

 of the reach of ordinary criticism. It can scarcely be compared, it 



* F. Koristka's Catalogue No. 11, Milan, 1903, fig. 45, p. 63. 



t ' Jena Glass and its Scientific and Industrial Applications,' by Dr. H. Hove- 

 stadt. Translated and edited by J. D. Everett, M. A., F.R.S., and Alice Everett, M.A. 

 Macmillan & Co., London, 1903, 8vo, xiv. and 419 pp., 29 figs. 



