Anchoring MollusJcs. 215 



Royal Society, No. 16, that gentleman affirms that " if a body 

 does not contain any repulsive elements, it cannot cause any 

 retardation in the movement of an impinging body ;" and other 

 reasons might be assigned to account for the small retardation 

 of moving bodies without assuming a tenuity calculated from 

 the known properties of atmospheric air. 



Mr. Bayma's theory is not the only one that might account 

 for the resistance offered by the space-atmosphere to a moving 

 body, not being proportionate to the actual quantity of matter 

 contained in a given bulk of it. What is called vis inertia is 

 not, as we have remarked in another paper, simply do-nothing- 

 ness, but the result of active forces, one of which is gravitation, 

 and we have certainly no right to assume that gravitation is an 

 attribute or property of matter under all conditions. It may 

 be one of an unknown number of correlative forces, and the 

 force which acts as gravitation under one set of conditions, may 

 appear in another character when the conditions are changed. 



These speculations may be dreams and nothing more ; but 

 a little dreaming is good for scientific progress, provided the 

 process of dreaming is not vainly conceived to be a process of 

 proof. 



As our object in publishing these conjectures is to stimulate 

 thought and inquiry, we will either print in extenso, or give an 

 account of any important communications we may receive on 

 any of the points discussed. 



ANCHOKING MOLLUSKS. 



BY W. NEWTON MACCAKTNET, 

 Cor. Secretary Glasgow Naturalists' Society. 



At the end of the last century the rage for conchology reached 

 its climax, and then slowly declined. In its place the study 

 of malacology engrossed the attention of many of those who 

 had only gathered shells for the beauty of their form and the 

 brightness of their colours. The possession of a cabinet of 

 shells fifty years ago (and in many cases, even now) did not 

 bestow upon the owner any knowledge of their structure or 

 habits, and it was only when he gathered, observed, and dis- 

 sected that he gained that essential knowledge which, while 

 benefiting himself, would help the progress of the science. 

 The shell to the conchologist may be of interest, but the 

 animal which inhabits the shell will give a more enduring 

 pleasure to the malacologist who studies its structure and 

 observes its habits. 



During the rage of shell- collecting, when a C armaria 



