404 London Electrical Society. 



refractive power as the epidermis, no light is reflected at the sepa- 

 rating surface of the water and the pores which contain it, so that 

 the light passes through the membrane, which thus loses its white 

 appearance. When the water escapes from the pores by evapora- 

 tion, or is driven from them by heat, the membrane again reflects 

 white light from the numerous surfaces of its pores. 



" As the colouring matter resides in the shell itself, its peculiar 

 colour is seen through the epidermis as distinctly where it is porous 

 as where it is not porous, when the porous portion has been ren- 

 dered transparent by the absorption of a fluid. 



" If we apply oil or varnish to the white pattern, we may oblite- 

 rate it permanently, or we may change it into a pattern entirely dif- 

 ferent from the original one. 



" If these observations appear to you to have any interest, you 

 are welcome to make any use of them you please. 



" I am, dear Sir, ever most faithfully yours, 



" D. Brewster." 



It will be observed, that Sir David Brewster points out how the 

 application of oil or varnish to the white pattern may obliterate it 

 permanently ; such a case has already happened more than once : 

 persons who have become possessed of some of the species whose 

 patterns are lost on immersion, not content with their natural 

 beauties, and unaware of their peculiarity, have had recourse to art, 

 and by applying oil or varnish, have spoiled their specimens, — a 

 proper punishment for trying to mend nature. 



LONDON ELECTRICAL SOCIETY. 



Oct. 19, 1841. — A Translation by the Secretary, of "Observations 

 on the Electrical Effects of the Gymnotus," by Professor Schcenbein, 

 was read. 



The author having related at some length the nature and re- 

 sults of certain experiments he made with the Gymnotus of the 

 Adelaide Gallery, proceeds to examine the reasons which have in- 

 duced some philosophers to attribute its electrical powers to the pe- 

 culiar physical or mechanical construction of the electric organ, and 

 adduces a mass of facts in proof that this organ bears very little 

 analogy to Volta's pile. For instance, it consists of a combination 

 of substances possessing naturally but a very feeble electromotive 

 power, and yet the fish will give shocks equal in force to those ob- 

 tained from a very large Leyden jar charged at its maximum, or from 

 200 pairs of a highly excited voltaic battery. Again, the creature 

 dwells in a conducting medium which completes at all times the 

 circuit between the poles of its organ, and yet no passage of elec- 

 tricity occurs but at its will ; it is precisely as if it possessed a 

 means of insulating or uninsulating the apparatus at pleasure ; al- 

 though physiologists have not detected any arrangement fitted for 

 such a purpose. The fish too can regulate the intensity of its 

 discharges at will ; this is especially evident when a comparison is 

 made between the effects produced by touching it with the human 

 hand, or through the medium of a metallic conductor. The power 

 evidently depends upon an intimate union, of which we know not 



