RECENT ADVANCES IN SCIENCE 635 



quantity of any aldehyde remain soft for forty-eight hours ; 

 ketones do not exert this action. 



GEOLOGY. By G. W. Tyrrell, A.R.C.Sc, F.G.S., University, Glasgow. 



General and Dynamical Geology. — A. P. Coleman's presidential 

 address to the Geological Society of America (Bull. Geol. Soc. 

 Amer. 191 6, 27, 175) deals with " Dry Land in Geology," and 

 discusses the arid and glacial land deposits of former geological 

 epochs. He believes in the essential permanence of the con- 

 tinental areas, although there has been perpetual and carefully 

 balanced oscillations on their margins. 



A new reading of the much-debated Hurlet sequence of the 

 Lower Carboniferous in the districts of Campsie and Kilsyth 

 (Stirlingshire) is proposed by Mr. David Ferguson (Trans. 

 Inst. Min. Eng. 191 6, 52, 7). He believes that the limestone 

 identified as Hurlet in this area really belongs to a much lower 

 horizon at the top of the Calciferous Sandstone lavas, and is 

 separated by unconformity from the strata of the Carboniferous 

 Limestone Series. The question is of some economic importance 

 as the limestone horizons form datum lines for the exploration 

 of the coal and ironstone seams of the Midland Valley of 

 Scotland. 



Mr. M. Macgregor, of the Scottish Geological Survey, has 

 accomplished an excellent piece of work in finally settling the 

 origin of the coarse breccias in the Jurassic of East Sutherland 

 (Trans. Geol. Soc. Glasgow, 1916, 16, 75). These consist of 

 angular blocks of Middle Old Red Sandstone, ranging up to the 

 enormous size of 1 50 x 90 x 30 feet, embedded in fossiliferous 

 marine Jurassic muds which are often waved and contorted 

 around the included blocks. These breccias are of very re- 

 stricted distribution, and have been attributed to river or ice 

 action, but Mr. Macgregor shows that they represent talus 

 deposits derived from Old Red Sandstone cliffs bordering the 

 Jurassic sea, similar to the deposits which must now be forming 

 along the Caithness coast. 



Petrology. — In a short criticism of Bowen's recent work on 

 magmatic differentiation (Journ. Geol. 1916, 24, 554) Dr. A. 

 Harker contends for differentiation in intercrustal basins 

 prior to intrusion rather than differentiation in situ, and shows 

 that large intrusive masses (e.g. gabbros and granites of Skye) 



