1908-1909.] 



I9i 



This species again bore out his statement that the last larval stage 

 was by far the longest, as its first two stages each lasted less than 

 a fortnight, while the third (final) stage occupied from five to 

 eight weeks. He succeeded in getting these larvae to spin up, 

 and after from nine to sixteen days the pupae hatched out into 

 beetles, the whole cycle having lasted about twelve weeks. He 

 pointed out that there was plenty of work yet to be done on this 

 species, and that there were hundreds of common water insects 

 which would give both amusement and information to any 

 amateur who chose to start a few small aquaria. 



The lecture was illustrated by a number of lantern slides, 

 mostly from drawings made by the lecturer. The paper was 

 spoken to by the following members : — the President, and 

 Messrs. J. Hamilton, W. J. C. Tomlinson, W. Gray, M.R.I.A., 

 and H. L. Orr. 



" THE DETERMINATION OF SPECIFIC GRAVITY, AND THE 

 USE OF HEAVY LIQUIDS." 



A meeting of the Geological Section was held on Wednesday 

 evening, January 27th, in the Museum, College Square North, 

 when Mr. Thomas Dewhurst, A.R.C.Sc. (Lond.), delivered an 

 interesting lecture on " The Determination of Specific Gravity, 

 and the Use of Heavy Liquids." A definition of specific gravity 

 was given, and emphasis was laid by Mr. Dewhurst on its value 

 as a determinative constant of mineral species. The specific 

 gravity of large specimens of minerals and rocks can readily be 

 obtained with the chemical balance, Penfield's wooden balance, 

 or Walker's steelyard balance. The spring balance of Jolly is 

 specially adapted for small specimens, while the specific gravity 

 bottle is used for sands and powders and for porous, friable, and 

 cavernous specimens. In the case of a small mineral particle the 

 specific gravity is determined with the aid of some heavy liquid, 

 such as Sonstadt's solution or Klein's solution, the density of the 



