ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
381 
prevent oxidation. Then polish with chamois, mount on a slide without 
a cover-glass, and examine. # . 
A thin coating of vaselin is the best protection from oxidation. 
Old Book on Optics. — The following figures (68-71) from Zahn’s 
‘ Oculus Artificial^ ’ (1702), to which Mr. E. M. Nelson referred at the 
meeting in November last,* have been made from photographs kindly 
taken for the purpose by Mr. C. L. Curties. 
Fig. 68. 
Fig. 68 illustrates a telescope-sight for a musket and a cannon. . Zahn 
says, C£ Bombardae et omni generi balistarum ac tormentorum bellicorum 
tubum opticum sive telescopium aptare, quo visus ad scopum exacte 
dirigi poterit.” 
Fig. 69 is the Jordan sunshine recorder. The legend in the ribbon 
below is 
“ Horas Luce Sono tibi sphaerula Yitrea monstrat, 
ignis nil mirum Coelicus urget opus.” 
The first thing that attracts attention is the converging nature of 
the sun’s rays incident on the sphere ! Next, it will be observed that 
* Journ. R.M.S., 1897, p. 600. 
