1892.] 



THE MICKOSCOPE. 



211 



92. Is there any dictionary or enclyclopedia which gives a 

 full correct definition of the word " sand'''' ? — H. E. C. 



H. E. C, or rather E. C. H., has written a pleasing little paper 

 on " Sand," to be found in the Am.Mon. Mic. Journal, vol. xi, 

 pge. 6S, and still seeks a definition for a ver}' diversified product 

 of geological activity. A mineral is distinguished by a more or 

 less definite chemical composition. A rock is a mass composed 

 of one or more minerals. Sand is pulverized r9ck from one or more 

 localities, distributed, modified, mingled and mixed by frost and 

 flood. Recent foraminifera, polycistina, and spicules are no more 

 a part of sand than are snail-shells or fish scales. 



93. Is there any reason why the binocular ?nicroscope should 

 not be preferred to the 7nonocular^ expense and size excepted;' 

 — Purchaser. 



The binocular has a limited use and with low powers only. If 

 one is to be purchased see that the prism is arranged to be entirely 

 removed, so the upright main tube may be wholly clear and allow 

 the use of wide-angle objectives, as a monocular microscope. 



94. Name three good books 07i the microscope for a beginner. 

 — Beginiier. 



The following are good, cheap, and well-illustrated books suit- 

 able for a beginner : 



Stokes. Microscopy for Beginners. A work devoted to pond 

 life. 



Phin. How to use the Microscope. Gives good descriptions 

 of the microscope and accessory apparatus, with directions for 

 mounting simple objects. 



M. C. Cooke. 1,000 Objects for the Microscope. A sort of 

 a small dictionary of microscopic objects. 



V/AYS 



AND MEANS 



Photomicrography of the Solar Spectrum and Absorp- 

 tion Spectra. — D. Joaquin Ma. de Castellarnau describes in 

 Cronica Scientifca., Barcelona., August, 1SS9, 7 pp. (sep. 

 copy), the method which he employs to obtain photomicrograms 

 of the solar spectrum. In the disposition of the microscope and 

 spectral eye-piece which he adopts a ray of sunlight is directed 

 by a Prazmowski heliostat upon a mirror, by which it is reflected 



