230 



Scientific Intelligence. 



e 2 



Gas burner 39 



Auer " No. __ 42 



" " No. 1 43 



" " No. 2 43-5 



Druminond light 48 



" " 60 



" " 60 



Magnesium " .' 107 



Electric arc, 8 amp. 106 



" 15 120 



" 17 125 



" 18 130 





Actinic degree. 



ei 



e 2 



39 



1-0 



u 



1-08 



a 



1-10 



tt 



1-12 



40 



1-20 



u 



1-50 



a 



1-50 



39 



2-72 



40 



270 



39 



3*08 



a 



3*2 



<< 



3*3 



II. Geology and Natueal History. 



1. Earth Movement ; by Charles R. Van Hise, Trans. Wis- 

 consin Acad. Sci., Art, and Letters, vol. xl, pp. 465-516, Jan., 

 1898. — The " gravitation theory " suggested by Prevost in 1840 

 is presented in this paper with great force and clearness in the 

 light of the science of to-day as the explanation of the various 

 phenomena of earth movement. Epeirogenetic, orogenic and 

 epigene movements are all alike shown to be gravitative. Vul- 

 canism, too, is referred to the same cause. The dominant force 

 which is behind the great regional extrusions of igneous material 

 is gravity. Further it has been noted that these extrusions are 

 contemporaneous with great crustal movements. The phenomena 

 may be considered under the headings of, vulcanism in connec- 

 tion with regional compressive movements, vulcanism in connec- 

 tion with regional tensile movements, and local vulcanism " (p. 

 497). "I would not underestimate the power of steam in vul- 

 canism, but that its expansive power is the chief force in the 

 transfers of liquid material within the earth seems to me to be 

 wholly unproved. The dominating force as explained is believed 

 to be that of gravity " (p. 502). 



The author explains the deep-seated flowage of material from 

 the oceanic basins landward in continental growth as follows : 



" It has been supposed that the regions below the sea have a 

 higher conductivity than the continents and their downward ex- 

 tensions. If this be so, the former regions would ever continue 

 to cool more rapidly than the latter, and would contract more. 

 Both of these contractions would result in concentration of the 

 rocks of the sea bed and in bringing them nearer to the center of 

 the earth than the continental masses. Hence gravity would be 

 more effective on the mass below the sea than elsewhere, and dif- 

 ferential stresses would result. The quantitative value of the 

 increased effectiveness of gravity on the mass of the sea beds 

 should be estimated upon various numerical suppositions, but the 



