348 Harrington — Interesting Variety of Fetid Calcite. 



Sir William Logan, judging from his description, regarded 

 the fetid calcite as a local modification of one of the great bands 

 of limestone belonging to the Grenville series. This modifica- 

 tion might have been due to some form of solfataric action 

 going on at the time of crystallization and introducing hydro- 

 gen sulphide, one of the usual accompaniments of such action. 

 The crystals of pale green tourmaline (a boron mineral) which 

 occasionally occur in the calcite might also point to solfataric 

 action, though no such assumption is necessary to account for 

 its presence. The hydrogen sulphide, again, might be taken as 

 an indication of the existence of organic matter in the old sedi- 

 ments of the Laurentian series ; for, as is well known, organic 

 matter in presence of w T ater reduces alkaline and earthy sul- 

 phates to sulphides, which reacting with water and carbon diox- 

 ide produce hydrogen sulphide. On the other hand, however, 

 the hydroden sulphide might have been produced from sul- 

 phides formed in the earth's crust quite independently of any 

 organic agencies. 



Associated with the fetid calcite there is also a white, trans- 

 lucent to subtranslucent quartz, which, on striking with a ham- 

 mer or scratching with a knife, likewise evolves hydrogen 

 sulphide. "When fragments of the quartz are heated in a test- 

 tube, considerable quantities of the gas are given off and readily 

 darken lead acetate paper. No attempt has been made to esti- 

 mate the proportion of the hydrogen sulphide in this case, nor 

 does there seem to be any simple way of accomplishing this. 

 In lump form the mineral would dissolve too slowly in hydro- 

 fluoric acid, while if powdered most of the hydrogen sulphide 

 would escape. On heating the fragments, too, only a portion 

 of the gas can be liberated and that in part at least is liable to 

 undergo dissociation at the temperature of the experiment. 

 The fluid-cavities in the quartz are, however, larger than in the 

 calcite and more readily admit of study. Most of them aiford 

 no visible evidence of the presence of more than one liquid, and 

 the moving bubble which they contain does not disappear on heat- 

 ing to 150° C — the highest temperature tried. In a few cases 

 the bubbles disappeared at from 32°-35° C, indicating, no 

 doubt, that the cavity contained liquid carbon dioxide whose 

 critical temperature is 32° C. In one case the critical point 

 was 40° C, and in several others from 60°-65°, indicating, 

 possibly, mixtures of carbon dioxide and hydrogen sulphide, 

 the critical point of the latter being about 100° C. In cases 

 where the bubbles did not disappear water is evidently pres- 

 ent, accompanied no doubt by hydrogen sulphide and possibly 

 by carbon dioxide as well. Some of the cavities, again, appear 

 to contain two separate liquids with a bubble in one of them. 



McGill University, Montreal. 



