NOTES. 101 



accordance with the law of geometrical progression, and that the 

 cessation of their growth is caused by the diminution of their 

 food supply." 



At the January meeting of the Geological Society {Quarterly 

 Jourfi. Geol. Soc, Li., pp. 196 — 209), Mr. E. B. Wethered read an 

 interesting paper on the formation of oolite. We have already 

 noted Dr Rothpletz' work on the oolitic granules from the Red 

 Sea and Great Salt Lake. Mr. Wethered's views are that "minute 

 fragments of remains of calcareous organisms — such as corals, 

 polyzoa, foraminifera, crinoids, etc. — collected on the floor of the 

 sea. These became nuclei, to which the oolitic-forming organisms 

 attached themselves, gradually building up a crust. Sometimes 

 this growth was concentric ; sometimes at right angles to the 

 nucleus of the two combined. When the growth was concentric, 

 other tubules frequently cropped up in other directions and crossed 

 the concentric tubules. At the same time calcareous material was 

 secreted, and the interstitial spaces between the tubules were filled." 



In the discussion arising from Mr. W^ethered's paper, Dr. G. J. 

 Hinde pointed out the striking similarity in the microscopic struc- 

 ture of the oolitic grains from Great Salt Lake to that of the 

 Palaeozoic and later oolites, and thought that " if the algal origin 

 of the former should be confirmed, there could hardly remain any 

 doubt that the latter was similarly derived." Prof. Judd said that 

 in 1862 Dr. F. Cohn "pointed out the important part played by 

 algae in the formation of the Sprudelstein of Carlsbad and other 

 calcareous rocks " ; that " Bornet, the French algologist, had 

 insisted no less strongly on the work done in perforation and 

 breaking up of calcareous fragments by other plants"; Prof Judd 

 " was inclined to regard some of the structures as due to the 

 action of destructive rather than to constructive organisms." 



A series of interesting experiments has lately been made on 

 some of the French railways with the use of inclined planes, or 

 " air-ploughs," for the purpose of lessening the air resistance 

 experienced by trains. We are told that by means of such an 

 apparatus a saving of coal, amounting in some cases to 8 or even 

 12 per cent., has been effected, but something must be deducted 

 for the excellence of the engine and its driver. We are rather 

 puzzled as to how M. Ricour makes the slanting planes '■'■four in 

 three" since, even if they were vertical, they would only be at an 

 incline of one in one ! Still, as we are informed that the Paris, 

 Lyons, and Mediterranean Company has had forty engines fitted 

 with these planes, the invention seems to be something more than 

 a mere theoretical speculation. 



