226 Scientific Intelligence. 



in general." The cementing silicic acid has divided itself off into 

 areas each of which has attached itself to one of the original 

 fragments, forming with it "a crystallographically single indi- 

 vidual. Thus the quartz grains enlarged themselves until they 

 mutually limited one another, and filled out all interstitial space, 

 so that their form naturally became that of irregularly angular 

 grains. The original form of the quartz grains is only now 

 recognizable by the dust upon their surfaces; without this dust 

 *- / the plastic nature of the rock would be completely obliterated, 

 and the whole appear as a crystalline granular quartz-aggregate." 

 It does not appear from this review that Tornebohm was dis- 

 posed to extend these conclusions to all ordinary quartzites, or 

 that he appreciated the similarity of origin of the quartzites and 

 so-called "crystallized" sandstones. 

 Washington, D. 0., January 28th, 1886. 



3. A Submarine Grater in the Atlantic near the Canaries. — 

 In a paper of much interest on " The North Atlantic as a Geolog- 

 ical Basin," by T. Mellard Reade (Presid. address to the Liv- 

 erpool Geol. Soc, 20 pp. 8vo, 1885), we find it stated, from infor- 

 mation received by Mr. Keade from Sir James Anderson, that 

 the inequalities of the bottom are very great between Lisbon and 

 the Canary Islands; that " off the Burlings we found a crater 

 nearly 1,000 fathoms deep, into which the cable [electric] ran, 

 and we had afterwards to recover and re-lay it ; on the top of 

 the crater were 80 fathoms soundings." " The depression is only 

 a few miles in diameter," while " all around it is under 100 fath- 

 oms." Valleys are abundant; "off the Burlings, 39° 25' 30" N. 

 and 9° 54' W., the ship had 1,300 fathoms under her bow and 

 sounding under the stern they got 800 fathoms." " Off Lisbon 

 and up to the edge of the soundings there are great inequalities, 

 which no doubt are due to a chain of mountains in the ocean. 

 The problem we have to solve when the cable is laid over such 

 places is by numerous soundings to trace out the valleys. Some- 

 times we succeed, but sometimes we do not, as often within half 

 a mile there are great inequalities, and it would be impossible to 

 sound the whole ocean every half mile." From these and other 

 facts maintained in his paper, Mr. Reade concludes that the 

 ocean's bottom is not as even in surface or gentle in its slopes, as 

 announced in some recent descriptions. 



4. Geological Sketch of the Island of Antigua • by E. C. 

 Purves. (Bull. Mus. Roy. d'Hist. Nat. de Belgique, Brussels.) 

 — This paper is accompanied by a colored plate and section show- 

 ing successive formations from southwest to northeast, the gen- 

 eral trend of them being northwest. They are, commencing to 

 the southwest : (1) various volcanic rocks, in hills 800 to 1200 

 feet high ; (2) Upper tufas which he proves to be of Miocene 

 age, with (a) Lower marine limestone with chert, (b) volcanic, 

 sand and conglomerate, and (c) chert, of freshwater deposition ; 

 (3) Upper limestone and marls with hills of 300 feet, and with a 

 narrow sea-border in part of recent horizontal marls. No. 1 and 



