388 Mr. Nicholjon's 'Oejcnpllon of a new hjinmenf 



if thofe fpaces be taken for abfolute weights; or, 

 at all events, it brings forward a rather intricate 

 confideration of the relation which the bulks of 

 the fpaces, or parts of the fi-em, have to the whole 

 immerfed part. This appears to have been the 

 inducement that led M. G. F'ahtenheit * to add 

 a final 1 difli or fcale to the top of the upper 

 flem, which, inftead of graduations, had only 

 a fin"-!e mark that, in ail cafes, Was to be brought 

 to the furface of the fluid, by means of weights 

 added in the faid fcale. 



Mr. Clarke, f who in the year 1730 publiflied 

 an account of an hydrometer, does not appear 

 to have been apprifed of what had been done 

 before by Boyle and Fahrenheit. For he fpeaks 

 of his own inftrument as a new invention, though 

 it does not differ from that of Boyle, except in 

 having a great number of ballaH: weights to be 

 fcrewed occafionally to the lower ftem, inftead 

 of depending on the graduations of the upper 

 ftem; and he affirms, that the fpecific gravities 

 of fluids cannot be found without a great deal 

 of trouble, though it is certain that they may 

 be found with greater eafe, and much more 

 accuracy, by that of Fahrenheit, than by his own. 

 Clarke's hydrometer, with weights adapted to 



* Reid and Gray's Abridgment of the Phil. TranC 

 vol. VI. part I. p. 294. 



t Ibid. vol. VI. part I. p. 295. 



allow 



