J. L. and H. D. Campbell — Geology of the Virginias. 193 



involving the contact angle should be greater than that obtained 

 from the height of bubbles, and that again greater than that 

 obtained from the rise in capillary tubes. No inequality of this 

 sort is apparent. 



The value of a 2 for alcohol, reduced to 0°. is 5*941. That 

 obtained by Quincke from the rise in capillary tubes is 5*906, 

 and that obtained by me from the method above mentioned, 

 which does not involve the contact angle, is 5*843. 



For olive oil the reduced value of « 2 is 7*602. Brunner 

 gives 7*461, Quincke 7*366 from the rise in tubes, and I ob- 

 tained, from the method mentioned above, 7*315. 



For petroleum the value of a~ at 0° is 7*034. Mr. Durell 

 obtained, from the rise in tubes, the value 7*204. The variable 

 character of petroleum renders a comparison with the results 

 given by other observers useless. 



The same remarks may be made on the comparison of results 

 for alcohol, olive oil and petroleum that have been already 

 made in the case of water. The discrepancies in the results 

 are not such as to lead to the conclusion that the assumption 

 of a zero contact angle is false, in the case of any of the four 

 liquids used. The difficulties offered by some of the methods 

 employed, and unavoidable differences in the materials used by 

 different observers, renders any positive statement at present 

 impossible. It is my hope soon to be able to present a con- 

 nected series of observations, which will perhaps lead to some 

 more definite conclusion. 



John C. Green School of Science, Princeton, N. J. 



Art. XIX. — Wm. B. Rogers's Geology of the Virginias. A 

 Review ; by J, L. and H. D. Campbell. 



(Continued from vol. xxx, p. 374.) 



In our further treatment of the subject before us, we shall 

 limit our remarks to the moat salient points in the higher 

 formations of the geological system of the Virginias, basing 

 them chiefly upon personal observations, and making them 

 supplementary to the comprehensive and able discussions 

 found in the volume under review. 



Niagara G?vup, IV, V, R. (5a, b, c and 6). — In Virginia this 

 comprehensive group consists of alternating beds of conglom- 

 erates, hard sandstones and shales — calcareous shales predomi- 

 nating in the upper portion, in which occasional beds of 

 impure limestone occur. In the State Reports the whole 

 series is described under two divisions, IV and V of Professor 



Am. Jour. Sci— Third Series, Vol. XXXI, No. 183.— March, 1886. 

 13 



