ZOOLOGY AND BOTANY^ MICROSCOPY, ETC. 



707 



in situ exhibited. Tlie heart will appear about a foot in length, and 

 will powerfully contract, stimulated by the heat. The heart may be 

 removed from the body, pinned to a card, and this thrown on the 

 screen, still there is vigorous motion. Again, the heart maybe halved 

 and quartered, yet still the pieces will be seen to contract. 



No complex or wonderful apparatus is required. " Two hundred 

 dollars and a little patience and ingenuity will go farther than some 

 fifteen hundred dollar outfits." 



Mr. E. Hitchcock,* on the other hand, considers that taking facts 

 as they are at present, it is certainly much better to use photo- 

 graphs of microscopic objects, taken either from the objects them- 

 selves by aid of the Microscope, or else from good woodcuts — which is 

 often the better plan — than to grapple with the difficulty of using the 

 projecting Microscope. " We regard the latter as a useful instrument 

 for popular demonstrations, and no doubt it has a limited sphere of 

 usefulness in more strictly scientific work, but until it is greatly 

 improved in several respects, it cannot be of very great value to 

 lecturers upon scientific subjects." 



Assyrian Lens. — Sir A. Henry Layard, in his ' Nineveh and 

 Babylon,' describes a lens which he found in the course of his excava- 

 tions, and which is now in the British Museum. By the kind per- 

 mission of Dr. Birch, the Keeper 



of Oriental Antiquities, we have Pj^ 23 j 



been enabled to figure it here 

 (figs. 131 and 132). 



The lens is thus referred to 

 by Sir A. H. Layard f:— " With 

 the glass bowls was discovered 

 a rock-crystal lens, with opposite 

 convex and plane faces. Its 

 properties could scarcely have 

 been unknown to the Assyrians, 

 and we have consequently the 

 earliest specimen of a magnifying 

 and burning glass. It was buried 

 beneath a heap of fragments of 

 beautiful blue opaque glass, 

 apparently the enamel of some 

 object in ivory or wood, which 

 had perished. Fig. 132. 



I am indebted to Sir David 

 Brewster, who examined the lens, for the following note: — 'This 

 lens is plano-convex, and of a slightly oval form, its length being 

 1-j^ in., and its breadth ly% in. It is about l-4th| of an inch 

 thick, and a little thicker one side than the other. Its plane 

 surface is pretty even, though ill polished and scratched. Its convex 



* Amer. Mon. Micr. Journ., iv. (1883) pp. 125-6. 



t 'Nineveh and Babylon,' pp. 197-8. 8vo, London, 1853. 



X "9-lOths" in original. 



