78 THE CANADIAN NATURALIST. [March 



that some geologists have erred : they have not made the neces- 

 sary calculations, and found by the known rule of arithmetic that 

 100.000,000 is to small a number to represent in years the pro- 

 bable age of the earth's crust ; but they look first at the 

 phenomena and then at the figures ; and as the two produce 

 totally difi"erent impressions, they pronounce the figures to be 

 too small to represent the phenomena. 



If the geologist could find a method of ascertaining the actual 

 rate at whiih these denuding agents do perform their work ; if it 

 could be ascertained at what rate the face of the country is at 

 present being denuded, how much, for example, per annum the 

 general level of the country is being lowered and the valleys 

 deepened, then we should have a means of ascertaining whether 

 or not the agents to which we refer were really capable of pro- 

 ducing the required amount ot change in the earth's surface in 

 the allotted time. But mere conjectures in the absence of some 

 positive determinations are worse than useless." 



Mr. Croll then proceeds to state that there is an available 

 method afforded by the measurable rate of denudation of our 

 continents by sub-aerial and oceanic agencies, and enters into 

 elaborate calculations as to this rate in different regions, and at 

 difierent geological times. The results are very curious and 

 interesting, but the completion of the series of papers, containing 

 the final conclusions of the writer, has not yet reached us. 



J. AV. D. 



Deep-Sea Dredging in Its Relations to Gteology. — 

 The proceedings of the Royal Society contain a most interesting 

 Report of Dr. Carpenter and Dr. Wyville Thomson, of dredgings 

 conducted by them in 1868, at depths previously reached only by 

 the comparatively inefficient means of the sounding line. In 

 their deepest dredgings, 650 fathoms, they brought up not only 

 Foraminiferoe, but sponges and star-fishes allied to Ophiura, thus 

 showing that a somewhat varied life exists at these great depths. 

 At this great depth, also, they found the calcareous mud of the 

 bottom penetrated and covered with that diffused protoplasmic or 

 sarcodic substance which Prof. Huxley has named Bathi/bius, 

 and which seems to be an organism even less specialised than the 

 ordinary Rhizopods, and to be, perhaps, a representative in the 

 modern seas of the primeval Eozoon of the Laurentian rocks. 

 Another remarkable discovery is that of the existence of a 

 minimum temperature of 32'^ Fahrenheit at the sea-bottom, in 



