July 18, 1884.] 



SCIENCE 



67 



The vein is at contact of a diabase country 

 on the one side, with a diorite on the other. 

 Mr. Becker finds evidences of repeated slip- 

 ping. Below, it probably cuts into the diorite. 

 The ore was derived from the eastern dia- 

 base country, in the augite of which, analysis 

 still finds the metals in small quantities. The 

 disseminated metals were leached out and car- 

 ried westward into the fissure, and there accu- 

 mulated. The solvent water was hot, and 

 contained alkaline carbonates and alkaline sul- 

 phides ; in other words, was solfataric. The 

 rocks were left in a widely decomposed con- 

 dition. These conclusions are confirmed by 

 the observations of others, as well as of Mr. 

 Becker himself, on the phenomena of deposit 

 of silica and metallic sulphides from solfataric 

 waters, now going on at Sulphur Bank and 

 Steamboat Springs. It is not unlikely that 

 the process is still going on also in Comstock 

 lode. 



On several points Mr. Becker differs from 

 previous observers. Richthofen, in his cele- 

 brated memoir on A natural system of igneous 

 rocks, gives a prominent place as a rock 

 species to propylite. Mr. Becker thinks, and 

 probably rightly, that propylite is only an 

 altered andesite, and therefore that the species 

 is untenable. Rosenbusch, however, had al- 

 ready shown that propylite must be regarded 

 as a modification of andesite, and Mr. Becker 

 ought to have stated this fact. 



Again Mr. Becker differs (and we think again 

 rightly) from Church as to the source of the 

 heat of Comstock lode. Church ascribed it 

 to kaolinization. Mr. JBecker shows the in- 

 sufficiency of this cause, and suggests as a 

 more probable cause solfataric action, the fee- 

 ble remnant of previous volcanism. 



The memoir of Mr. Irving on the copper- 

 bearing rocks of Lake Superior deals with some 

 of the most vexed questions in geology. When 

 such men as Hunt, Whitney, Selwyn, Wads- 

 worth, and Irving differ as to the age and 

 stratigraphic relations of the copper-bearing 

 series, those who have not personally examined 

 the ground have no right to an opinion. Mr. 

 Irving' s view is, that this series partly fills the 

 great gap between the Huronian and the Cam- 

 brian. It consists of sandstones and conglom- 

 erates, with interbedcled sheets of igneous 

 rocks, mostly basic ; the whole being of enor- 

 mous thickness. 



As to the mode of occurrence and origin of 

 the ore, there is a resemblance to, yet striking- 

 difference from, that of Leadville. As in Lead- 

 ville, so here, we have alternating sheets of 

 strata and lava ; also, in both, the ore seems 



to have been leached from the igneous, and 

 gathered in fissures, cavities, water-channels 

 of any kind in the intervening strata, by means 

 of down-percolating water ; also, in both, the 

 deposit seems to have been made by substitu- 

 tion ; although the explanation of the substi- 

 tution is more difficult in this case. But, on 

 the other hand, the age of the strata is pre-Cam- 

 brian instead of carboniferous ; the strata are 

 conglomerates and sandstones instead of lime- 

 stones ; and the intercalary beds are contempo- 

 raneous instead of subsequent, i.e., poured out 

 on the surface, and covered with sediments, in- 

 stead of forced between the strata. As to the 

 obscure question of the reactions by which ore 

 was deposited, the author seems to adopt Pum- 

 pelly's view, that the copper was carried in 

 solution as sulphate, and was reduced by the 

 iron of the basic rocks, which oxidized itself 

 at the expense of the copper sulphate. 



The memoir of Hague on the Eureka dis- 

 trict does not touch the mines of this district : 

 that is left for a future memoir. It is con- 

 fined wholly to descriptive geolog}\ As such, 

 although not entertaining popular reading, it 

 is a model of painstaking, conscientious work. 

 It is on such work, and such only, that a true 

 geological science must be built. Only one 

 point we have time to notice. Mr. Hague de- 

 clares that there is no trachyte at all among 

 the western eruptive, what has gone under 

 that name being andesite. This decision is 

 founded on the fact that plagioclase is the 

 dominant felspar in all of them. The fact 

 admitted, the decision seems well founded. 

 But surely some consensus of view as to the 

 basis of classification of eruptive is devoutly 

 to be wished for. Shall it be the look and 

 habit, or mode of occurrence, or mineral con- 

 stitution, or age, or all these together? When 

 shall order come out of this chaos ? 



It is a pity that Mr. Chamberlin's paper on 

 the second glacial moraine comes last among 

 the geological articles ; for we are pressed for 

 room, and the subject is to us a specially invit- 

 ing one. The author commences his work by 

 trying to remove the confusion which exists oil 

 the subject of drift-deposits. He makes three 

 kinds of till : viz., 1, subglacial or true till ; 2, 

 englacial or superglacial till (a looser top 

 material) ; 3, subaqueous till, often confounded 

 with the first, but deposited by floating ice. He 

 also distinguishes between "osars and kames. 

 After many other distinctions which deserve 

 studious attention, he describes the peculiar 

 structure and appearance of terminal moraines, 

 and then applies these principles to the iden- 

 tification and tracing of the second glacial, or 



