14:6 Royal Society ': — 



is no evidence to show that these colourless shells have developed 

 any materials capable of manifesting colour after exposure to the 

 influence of light ; whereas my own and other experiments show 

 that the etiolated stalks and leaves of plants speedily manifest the 

 characteristic colour of the chlorophyl if placed in the sun's rays. 



So far, therefore, as our present knowledge on the subject justi- 

 fies any conclusion, the varieties of colour and the absence of colour 

 in the molUisks are physiologically separated from the phenomena of 

 etiolation in plants, and may be placed in the same category as the 

 varieties of colour and the absence of colour in the corolliis of 

 flowers, which depend upon the development of materials having 

 certain optical properties. 



Tlie beautiful facts observed by Prof. Forbes, instead of bejng 

 regarded as the consequence of imperfect exposure to light, must, I 

 think, take rank with the phenomena of coloration observed through- 

 out the animal kingdom, such as the peculiar markings of reptiles, 

 birds, and wild animals, according to their different habitats and 

 modes of life ; the colours of the upper and lower surfaces of fish, 

 and the like ; which cannot be shown to depend upon the exposure 

 or non-exposure to light with which they frequently, but not always, 

 coincide. These facts appear only to form a part of the vast and 

 perfect plan of creation, in which everything that exists is suited in 

 every particular to the conditions of its existence ; thus, those mol- 

 lusks which are designed to inhabit depths scarcely permeable to 

 light, can have no need, and hence have no provision, for elements, to 

 the manifestation of which light is an essential condition. 



" On the Intensification of Sound through Solid Bodies by the in- 

 terposition of Water between them and the distal extremities of Hear- 

 ing-Tubes." By S. Scott Alison, M.D., Assistant-Physician to the 

 Hospital for Consumption. 



In this Paper the author gives an account of various experiments 

 which he has recently made on sounds proceeding through solid 

 bodies. He has found that sounds which are faint, when heard by 

 a hearing-tube applied directly to solid sounding bodies, become 

 augmented when water is interposed between these bodies and the 

 distal extremity of the hearing-tube. He has been able, by the em- 

 ployment of water, to hear the sound of a solid body, such as a 

 table, which, without this medium, has been inaudible. Experi- 

 ments have been made upon water in various amounts and in dififerent 

 conditions. Thus a very thin layer, a mere ring round the edge of 

 the hearing-tube, masses of water in larger or smaller vessels, and a 

 bag of water, have been employed. The results have been the same 

 as regards augmentation. The degree of augmentation was greatest 

 when the hearing-tube was immersed freely in water. In experi- 

 menting upon water in vessels, it was found necessary to close 

 the extremity of the tube to be immersed, by tying over it a piece of 

 bladder or thin india-rubber ; for the entrance of water into the in- 

 terior interfered greatly with the augmentation. 



The effect of water in augmenting sound is materially reduced if 



