On the Mechauifm of the Eye. 337 



Fig, 42, 44. Shadow of parallel wires in the image of a diftant poiitt, \#hen the eye is 

 relaxed. ' 



Fig. 43, 45. The fame fhadows rendered curved by a change in the figure of thecry- 

 ftalline lens. 



Fig. 46. The order of the fibres of the human cryftalline. 



Fig. 47. The divifion of the nerves at the ciliary zone; the fclcrotica being removed. 

 One of the nerves of the uvea is feen paffing forwards and fubdlviding. From the calf. 



Fig. 48. Ramifications from the margin of the cryftalline lens. 



Fig. 49. The zone of the cryftalline faintly feen through the capfule. 



Fig. 50. The zone raifed from its fituation, with the ramifications pafiing through it 

 into the lens. 



Fig. 51. The zone of the cryftalline detached. 



Plate XV. Fig. 5X. The crenated zone, and the globules regularly arranged on the 

 cryftalline of the partridge. 



Fig. 53. The order of the fibres in the lens of birds and fifties. 



Fig. 54. The fegments of the capfule of the cryftalline turned back, to fliew the de- 

 tached ciliary procefles. From the calf. 



Fig. 55. Part of the choroid of the cod-fifh, with its red fubftance. The central artery 

 hangs loofe from the infertion of the nerve. 



Fig. 56. 1-he membrane covering this fubftance internally, raifed by the blow-pipe. 



Fig. 57. The appearance:of the red fubftance, after the removal of the membrane. 



IV. 



E-xperiments on the Chemical ProduBlon and Jgency of Ele£lridty. By William Hyde 



WoLUASTos, M. D. F. R. S. * 



Nc 



OTWITHSTANDING the power of Mr. Volta's eleftric pile is now known to be 

 proportional to the difpofition of one of the metals to be oxidated by the fluid interpofed, a 

 doubt has been entertained by many perfons, whether this power arifes from the chemical 

 aftion of the fluid on the metal, or, on the contrary, whether the oxidation itfelf may not 

 be occafioned by eleftricity, fct in motion by the conta£t of metals that have different con- 

 ducing powers. 



That the oxidation of the metal is the primary caufe of the eleftric phenomena obferved* 

 is, I think, to be inferred from the following experiments, which exhibit the galvanic 

 procefs reduced to its moft fimple ftate. 



Experiment I. If a piece of zinc and a piece of filverhave each one extremity Immerfed 

 in the fame veffel, containing fulphuric or mirriatit; acid diluted with a large quantity of 



- • Phil. Tranf. for 1801, p. 4i.'7. 

 Vol. V. — December 1801. Xx . water, 



