34 



SCIENCE. 



[N. S. Vol. XI. No. 262. 



in the Comptes Rendua. The composition is 

 found to be wholly different from that of 

 Chinese porcelain, and hence it would appear 

 that the manufacture of true porcelain was 

 known to the ancient Egyptians. The duplica- 

 tion of this Egyptian porcelain would require 

 40 parts blue glass, 50 parts fine sand, and 5 

 parts white clay. 



Le Chateliee has also examined statuettes 

 from Egyptian tombs which were supposed by 

 Salv6tat to be carved from a natural grit and 

 then glazed with a sodium-calcium-copper sili- 

 cate. It appears, however, that the statuettes 

 from several different localities consist chiefly 

 of fine grains of quartz sand, with a little clay 

 as a binding material. The glaze is a mixture 

 of sand with a sodium-copper silicate. 



The effect of sulfur, especially as pyrites, 

 in coal when used as a fuel is discussed by 

 Wilhelm Thorner in the Chemiker-Zeitung. 

 With such a fuel, not only sulfur dioxid, but also 

 sulfuric acid will be present in the combustion 

 products. Since at least a portion of this sul- 

 furic acid will be deposited upon the boiler 

 walls, tubes, etc., it is necessary that these 

 should be cleaned frequently. The more 

 moisture present, the greater the corrosive 

 action of the acid. If lime is mixed with the 

 coal, the formation or at any rate the deposition 

 of the acid is in large part prevented. The 

 author suggests the use of briquettes made of an 

 intimate mixture of coal with a little lime. 

 With these not only can fine coal screenings, 

 slack, etc., be used, but sulfuric acid corrosion 

 may be practically avoided. 



J. L. H. 



CURRENT NOTES ON PHYSIOGRAPHY. 

 In resuming the preparation of these notes 

 after an interruption of a year and a half, it 

 will not be possible to mention all the physio- 

 graphic essays published in the interval, but the 

 effort will be made to give account of the more 

 important ones in which the readers of Science 

 may be interested, as well as to review current 

 publications. 



GLACIAL SCULPTUEE IN WESTERN NEW YOEK. 



GiLBEET concludes that the Niagara lime- 

 stone upland in western New York is chiefly a 



product of pre-glacial erosion, but that its re- 

 lief has been increased by the greater glacial 

 erosion of the lowland underlaid by weaker 

 shales on the north, and that its northward- 

 facing escarpment has been modified in detail 

 by glacial action. Where the escarpment faces 

 northwesterly, so that the ice sheet moved 

 about parallel to its front, the outline has been 

 smoothed ; where it faces northeasterly, against 

 the ice motion, preglacial irregularities are in- 

 tensified by glacial scouring. The plain of 

 Medina shale bordering Lake Ontario, and now 

 overspread with drift and lacustrine strata, has 

 a broadly furrowed rock floor, with troughs 

 parallel to the ice motion : here the minimum 

 estimate of the general reduction of the surface 

 by glacial erosion is set at 40 or 50 feet, 10 or 20 

 times its measure on the limestone upland 

 (Bull. Geol. Soc. Amer., X., 1899, 121-130). 



GLACIATED VALLEYS. 



The most original physiographic essay pre- 

 sented to the recent International Geographical 

 Congress at Berlin was one by Penck on the 

 over- deepened valleys of the Alps. Not only 

 where large lakes occur near the margin of the 

 mountains, but far inward along the larger 

 rivers, the main valley floors are deepened be- 

 low the level of the side valley floors and the 

 discordance thus indicated is ascribed to the 

 stronger glacial erosion in the main than in the 

 side valleys. The side streams plunge down 

 into the main valley as waterfalls. This dis- 

 cordance of valley floors at flrst seems excep- 

 tional, characterizing valleys of glacial erosion 

 but not of river erosion : but it was well shown 

 that there is no such failure of analogy. A 

 river of water moves nimbly ; its cross section 

 is small and its channel is a small part of its 

 valley ; the river bed is usually hidden, and 

 hence, as main and side streams have the same 

 surface level at their junction, we do not ordi- 

 narily notice that the bed of the main river 

 channel is deeper than that of a side stream, 

 although this relation must be recognized as 

 soon as attention is turned towards it. A river 

 of ice moves slowly ; its cross section is large 

 and its channel is a large part of its valley ; 

 ancient glacial channels are now habitually laid 

 bare, and the discordance between the beds of 



