Bouv£.] 6 [January 2, 



the crystallized mineral, the white, the yellow of different shades, 

 the smoky, and the Amethyst. Now to appreciate the importance 

 of such a presentation it is only necessary to show that by a like 

 accurate one given of the Beryls used in jewelry it is possible to 

 distinguish the one species from the other by weight, which can- 

 not be done if it is assumed that the variation of the specific 

 gravity is as given in the mineralogical works ; for if Quartz is 

 taken to have a range of from 2.5 to 2.8 and Beryl 2.6 to 2.74, 

 there is, of course, no distinguishing them by this means. If, on 

 the contrary, the heaviest of the Quartz stones never have the 

 specific gravity of the lightest Beryl, the discrimination is easy. 

 This I feel quite sure is the case, though of course I am unwill- 

 ing to state that there will not be found stones that may prove 

 exceptional. I have weighed too many, however, not to have 

 full faith in the conclusion I draw from my figures ; namely, that 

 Quartz gems never weigh 2.67 and that Beryls including the 

 Emerald, the aqua marine, and the yellow and white varieties 

 which have a varying specific gravity of from 2.684 to 2.74 never 

 fall below the former figures, whilst the greater number weigh 

 over 2.7. Thus though the limits of variation approach each 

 other, they yet seem to be clearly distinct. The cases, indeed, 

 are exceedingly exceptional where the divergence is not greater, 

 only, as stated, two instances being noticed in a multitude of 

 examinations. 



Dr. S. Kneeland read a paper, illustrated by the stereopticon, 

 on the subsidence theory of earthquakes as evidenced by the 

 Ischian catastrophes of 1881 and 1883. 



After showing that there is no necessary connection between 

 the volcano and earthquake, other than that both are the effects 

 of one great cause ; namely, the contraction of the earth's crust 

 on the cooling nucleus and the consequent motion and develop- 

 ment of heat by the sinking masses — as suggested by Mallet — 

 he alluded to proofs which had come under his observation in the 

 Sandwich and Philippine Islands, Iceland, and the Mediterranean 

 basin, that almost all extended modern earthquakes have been the 

 result of subsidence and not explosions. He instanced Japan, 

 Lisbon, Port Royal, Java, Kilauea, Thingvalla, Taal, Val del 

 Bove, Missouri, the Yosemite Valley, and finally Ischia. He then 



