430 



SCIJENCE. 



[Vol. I., No. 15. 



California is not by any means 'established.) The 

 following approximate estimates of the quantity of 

 coal underlying one square mile of counti-y in several 

 localities have been made: — 



3{aiii seam, in vicinity of Coal Banks, Belly River, 

 5,500,000 tons. 



Grassy Island, Bow River (continuation of Belly 

 River, main seam), 5,000,000 tons. 



Tlorse-shoe Bend, Bow River, 4,900,000 tons. 



Blackfodt Crossing, worl<able coal in seam as ex- 

 posed on Bow River, 9,000,000 tons. — ( Geol. svrv. 

 Can.) J. B. M. [881 



Triassic traps and sandstones. — Mr. W. M. 

 Davis last summer visited a nimiber of localities in 

 Massachusetts, Coimecticul, and New Jersey, for the 

 purpose of studying the relation of the trap masses to 

 the triassic sandstones and shales. Some of these 

 are dikes ti-aversing the strata at high angles, and 

 about such there has been comparatively little con- 

 flict of opinion. But the greater number exist as 

 sheets conforming to the bedding; and these have 

 been regarded by some writers as contemporaneous, 

 by others as intrusive. Mr. Davis iinds distinct 

 evidence that some of the sheets were extravasated 

 during the deposition of the strata, being afterward 

 buried as the sedimentation progressed; and he finds 

 equally distinct evidence that other sheets were 

 injected between sedimentary layers already formed, 

 and cooled under pressure. To the first class belong 

 the principal masses of the Connecticut valley, includ- 

 ing Deerfield Mountain, Mounts Tom and Holyoke, 

 and the Hanging Hills near Meriden ; to the second, 

 belong the East and West Rocks near New Haven, 

 and tlie Palisades of the Hudson. The principal 

 intrusive masses occur in what are regarded as the 

 lower portions of the formation, and may have been 

 injected while tlie upper strata were still in process 

 of formation. 



A duplication of trap-ridges by faulting is demon- 

 strated in some instances, and suspected in others; 

 and it is pointed out that these faults may belong to 

 a wide system, whose total effect is greatly to expand 

 the outcrop of the formation by duplication. Each 

 of the greater triassic districts presents a wide ex- 

 panse of strata, with a prevailing dip at a consid- 

 erable angle in one direction. To account for the 

 phenomena by tilting alone, assumes an amount of 

 deposition and subsequent erosion appalling even to 

 the geologist; while the erosion demanded by the 

 hypolhesis of tilting and faulting combined is readily 

 admissible. 



The observations are prefaced by a bibliography of 

 the subject, and followed by a general discussion, 

 which includes an excellent digest of the opinions 

 and observations of earlier writers. The paper makes 

 a pamphlet of sixty octavo pages, illustrated by three 

 plates. — (Bull. nms. comp. zooL, rjeol. ser., i., no. ix.) 

 o. K. o. [882 



Ore-deposition by replacement. — As a result 

 of his geological studies in Leadville, Col., Mr. S. F. 

 Emmons has reached the conclusion tliat the ' car- 

 bonate deposits' of that locality were not formed by 

 the filling of pre-existent cavities. Tliey belong to a 

 class of deposits for which he proposes the name 

 metamorp/iic, and which are produced by a metaso- 

 raatic interchange between exotic matter and original 

 rock material. In Leadville the original rock is a 

 dolomitic limestone, 1.50 to 200 feet thick; and the re- 

 placement has occurred either at or near its contact 

 with an overlying sheet of porphyry. The introduced 

 or vein material consists of silica and metallic miner- 

 als. These were brought in solution by percolating 

 waters, having been previously dissolved from the 



associated eruptive rocks. In places the whole bed of 

 limestone has been replaced, but hi general only a 

 portion. Tbe equivalent vein occupies less space 

 than the limestone; but, allowing for this diffei'ence, 

 the thickness of vein and the thickness of residual 

 limestone are comijlementary. 



Mr. Emmons regards the class of metamorphic de- 

 posits as an extensive one, including a large propor- 

 tion of the so-called fissure-veins, both calcareous and 

 siliceous, of the Rocky Mountain region. — (P/m7. soc. 

 jVash.; meeting April 7). [883 



MINERALOGY. 



Products of the alteration of corundum. — 



The following are the results of observations made 

 by F, A. Genth: — 



Alteration into spinel. — At the Charter mine, 

 Madison County, N.C., corundum occurs crystallized, 

 and in cleavage masses of a grayish or while color. 

 In the cracks of the same it can be noticed that a 

 change has taken place; and in many cases Ihis ex- 

 tends through large masses, converting the corundum 

 into a massive greenisli-black spinel, rarely showing 

 octahedral crystals. Tbe same has a gravity of ^.7.51. 

 Scales of prochlorite, into which the mineral finally 

 passes, ai'e often present. Analysis of the carefully- 

 selected material indicates that it has the composition 

 of a spinel. 



Alteration into zoisite. — At Towns Coimty, Ga., 

 pink crystals of corundum are found, surrounded by 

 greenish-white cleavable zoisite. 



Alteration into felspar and mica. — The author cites 

 many occurrences in which cleavable masses of oligo- 

 clase and albite surround a core of undecomposed 

 corundum, also where the corundum is surrounded 

 by flat, cleavable mica (muscovite) or a delicate 

 fibrous mica (daraourite). Sometimes the mica and 

 felspar occur together; and the nucleus of unde- 

 composed corundum appears on its exterior very 

 rough, as if it had been eaten into. Numerous analy- 

 ses are given to prove the identity of the decomposi- 

 tion products. 



Alteration into margarite.^ This occurs more sel- 

 dom than the alteration into potash mica; and in 

 some cases scales of the latter are interposed between 

 the margarite, which usually is compact in its nature. 

 Specimens showing this alteration are from Jackson 

 and Iredell counties, N.C., and from Unionville and 

 Aston township, Penn. 



Alteration into Jibrolite. — Specimens from near 

 Norwich, Conn., and Burke county, N.C., show radi- 

 ated fibrolite surrounding crystals of unaltered corun- 

 dum. It seems as if, in many cases, the fibrolite 

 had undergone a subsequent change into mica. 



Alteration into cyanile. — At Iredell and Wilkes 

 counties, N.C., bladed cyanite is found surrounding, 

 and evidently resulting from, the alteration of corun- 

 dum. From the latter locality the cyanite has par- 

 tially undergone a change into micaceous minerals. 

 — {Proc. Anter. phil. soc. Philad., xx. 3S1.) s. i.. p. 



[884 

 GEOGRAPHY. 

 (Arctic.) 



Geographical notes from the north. — The 

 record of the Eira expedition appears in the Monthly 

 record of geography for April, giving an account of 

 the voyage up to Aug. 21, ISSl.^vhen the vessel was 

 pierced by the ice, and the subsequent proceedings 

 of the party until their rescue during the following 

 summer. Even during the arctic winter, warm south- 

 erly gales occurred, which resulted in limited areas of 

 open water. Prof. Nordenskiold's expedition will 



