Mr Conneil on the Chemical Constitution of Gadolinite. 303 



Yttria, 36.64 



Glucina, 6.90 



Protoxide of Cerium, .... 14.31 



Protoxide of Iron, . . . . 14.41 



Silica, 27.10 



Lime, .45 



98.71 

 From the smaller specimen, the locality of which was uncertain, 

 but which I have reason to believe was Broddbo, I also obtained 

 a quantity of glucina, although its proportion was not deter- 

 mined. With respect to that from Finbo, I cannot speak with 

 absolute certainty, on account of the very small quantity of 

 matter examined ; but from the examination made of it, I have 

 very little doubt that it also contained this earth. 



From these researches, therefore, as well as from those of 

 Ekeberg, Thomson, and Steel, it is sufficiently clear that glucina 

 is at least a frequent constituent of gadolinite. It would appear, 

 however, that the relative proportions of its several constituents 

 are subject to variation ; and it would be very desirable that any 

 person who could procure a sufficient quantity of crystallized 

 specimens from different localities, should execute a careful 

 analysis of them. 



DescriptioTt of a New Detached Pendulum Escapement ; invent- 

 ed by Alexander Witherspoon, Watchmaker, Tranent,* 



Considering the great variety of the escapements which have 

 already been devised, it may appear difficult, if not impossible, 

 to propose any other constructed on principles entirely new ; yet I 

 flatter myself, that that which I am about to lay before the Society 

 of Arts will be found to possess more simphcity, and to approach 

 nearer to perfection, than any which has yet been described. 



To obtain a correct notion of the advantages expected from 

 it, it may be proper to glance at the general principles according 

 to which instruments for measuring time are constructed. 



Both in clock and in watch movements, time is measured by 

 the oscillations of a body impelled towards a position of rest by 

 a force which increases with its distance from that central posi- 

 tion. In watches, this force, being supplied by the flexure of 



• Read before the Society of Arts, 13th April 1831. 



