560 Reviews — Dr. T. Sterry Hunt's Chemico- Geological Essays. 



ferous veins in other strata. He rejects the notion of intense heat, 

 sublimation, and similar hypotheses. This theory may be a good 

 one, but some of the arguments adduced in support of it will hardly 

 bear examination. Speaking of the solubility (p. 231) of the salts 

 and oxides of copper, lead, and silver, he asks why they do not 

 accumulate in the sea-water like the salts of sodium. Most chemists 

 would have thought that the sparing solubility of the chlorides of 

 the two latter metals, especially of silver, was quite sufficient to 

 account for the phenomenon ; but when a chemist has at command 

 the universal alkahest, he cares but little for a table of solubilities. 



The most important paper in the collection is " The Geognosy of 

 the Appalachians and the Origin of Crystalline Eocks" (xiii. p. 239), 

 an address delivered on retiring from the office of President of the 

 American Association for the Advancement of Science in 1871. 

 Without following the author into the intricacies of Transatlantic 

 geognosy, we must now consider Dr. Hunt in his capacity of geologist, 

 merely remarking by the way that the references in this paper 

 are necessarily of great value to those interested in American geology. 

 At this time he viewed the Taconic system, as defined by Emmons, 

 to constitute the true base of the Palaeozoic column ; but in the preface 

 to the second edition he seems to draw an important distinction 

 between the Upper Taconic and Taconian (see also Geol. Mag. 1879, 

 p. 519). It is of some importance to ascertain where he would 

 draw this base-line, as immediately below come his four great 

 groups of crystalline rocks, and it appears that we are threatened 

 with other groups, " since it is by no means certain that the 

 whole of the crystalline stratified rocks of New England are 

 included in the above" (p. 281). 



It would be unfair perhaps to dwell too much on the remarkable 

 change of front exhibited by Dr. Sterry Hunt in his interpretation 

 of the crystalline series above the Laurentians. We know that in 

 1861 he wrote that "the Green Mountain Gneissic formation, instead 

 of being beneath the Silurian series, is really a portion of the Quebec 

 group more or less metamorphosed, so that we recognize nothing in 

 New England, or South-east Canada, lower than the Silurian system " 

 (Can. Nat. vi. 93). In the two succeeding volumes he enlarges on 

 this topic — the Montalban (now placed by Hitchcock below the Huro- 

 nian) at that time figuring as metamorphosed strata of Upper Silurian 

 and Devonian age. It is probable that Hunt at this period, with his 

 usual impetuosity, was reflecting the views of others rather than re- 

 cording his matured convictions, and it is singular, to say the least, 

 that one holding the views on chemical geology which he seems then 

 to have held could ever have given his adhesion to such a piece of 

 epigenic metamorphism. And yet, as may be gathered from what 

 he says with respect to the origin of granitic veinstones, and still 

 more of metalliferous deposits, he is prepared to admit an amount of 

 circulation, both greater and lesser, throughout the rocks, which, 

 with the aid of the alkahest or universal menstruum, must be capable 

 of producing not only molecular but metasomatic changes which 

 shall meet all the requirements of the most advanced transmuta- 



