Royal Institution. 315 



The rocks of the Longmynd that have yielded the fossils referred to 

 are nearly vertrical beds of hard flaggy sandstone, coinciding in strike 

 with that of the Longmynd, and about \\ mile east of the principal 

 ridge. These beds form part of a series of bluish-grey sandstones, 

 alternating with purplish slaty beds, all of which lie below the con- 

 glomerates and red sandstones of the Portway, and above the thick 

 series of dark-olive schists, seen at Church Stretton, &c., which are 

 the lowest portion of the Longmynd series. 



Of the Annelid traces, some (which the author has referred to 

 Arenicola didyma) were found at Stretton, Callow Hill, and other 

 spots in the upper portion of the sandstone above mentioned, where 

 it is flaggy, rippled, and micaceous. Annelid tubes or tracks were also 

 found at Callow Hill in the same rock. The most interesting of the 

 fossils from this sandstone, however, are the indications of fragments, 

 cephalic (?) and caudal, of a trilobite allied apparently to the 

 Deikelocephalus of Dr. Owen. To the Longmynd Trilobite Mr. 

 Salter has given the name of Palmopyge Ramsayi. It occurred at 

 Little Stretton, &c. The author also described in detail some of the 

 surface-markings of the flags, which he referred to ripples and littoral 

 . action. 



ROYAL INSTITUTION OF GREAT BRITAIN. 



January 25, 1856. — "Inferences from the Negation of Per- 

 petual Motion." By W. R. Grove, Esq., Q.C., F.R.S., M.R.I. 



Scattered among the writings of philosophers will be found allu- 

 sions to the subject of perpetual motion, and here and there are 

 arguments like the following ; such a phsenomenon cannot take 

 place, or such a theory must be fallacious, because it involves the 

 idea of perpetual motion : thus Dr. Roget advanced as an argument 

 against the contact theory of electricity, as originally propounded, 

 that if mere contact of dissimilar metals, without any chemical or 

 molecular change, could produce electricity, then as electricity could 

 in its turn be made to produce motion, we should thus get per- 

 petual motion. 



It may be well to define, as far as such a definition is possible, 

 what is commonly meant by the term perpetual motion. In one 

 sense, all motion, or rather all force, is perpetual ; for example, if a 

 clock weight be wound up, it represents the force derived from the 

 muscles of the arm which turns the key ; the muscles again derive 

 force indirectly from the chemical action of the food, and so on. 

 As the weight descends, it conveys motion to the wheels and pen- 

 dulum ; the former giving force off" in the form of heat from friction, 

 the latter communicating motion to the air in contact with it, thence 

 to the case of the clock, thence to the air of the room, — proved 

 in a very simple manner by the ticking heard, which is, in fact, a 

 blow to the organ of hearing. Although ultimately lost to our senses, 

 there is no reason to suppose that the force is ever in fact lost. 

 The weight thus acting, reaches the ground quietly, and produces 

 no effect at the termination of its course. 



Y2 



