Geology and Natural History. 197 



ford's data. The latter states that this could have been done 

 with but small expenditure of time and in this article makes such 

 an application. It is shown that for an\ r assumed depth of com- 

 pensation a degree of compensation can be calculated which will 

 give the observed deflection of the vertical at any station. He 

 points out, however, that on assuming a certain depth of com- 

 pensation the degree of compensation is greatly different for 

 different stations, there being overcompensation for some, under- 

 compensation for others. This discordance of results Hayford 

 holds to prove the error of the criticism of Lewis. The results of 

 gravity determinations Hayford further points out to be in agree- 

 ment with his computations from deflections of the vertical, the 

 two methods of investigation thus giving mutual support. 



J. B. 



6. Investigation of the Theory of Isostasy in India ; by 

 Major H. L. Crosthwait, R.E., Dy. Superintendent, Survey of 

 India. Professional Paper No. 13, Survey of India. Pp. 14, pi. I. 

 1912. — This paper consists of an application to India of Hay ford's 

 method of determining the depth and degree of isostatic compen- 

 sation. It was assumed that compensation is uniform and com- 

 plete at a depth of 113*7 km., the depth found most probable for 

 the United States. It is shown that the residuals, the test of the 

 accuracy of the initial assumptions, average about three times as 

 large for India as for the United States. In conclusion Major 

 Crosthwait states that the drawback to treating this subject by 

 hard and fast mathematical formulae is that we introduce into a 

 discussion of the constitution of the earth's crust a uniform 

 method when, in reality, probably no uniformity exists. The 

 map of India in the back shows graphically the system in the 

 distribution of the residuals. The narrow trough of greatly 

 deficient density lying south of the Himalayas is a most striking 

 feature. J. b. 



7. Effect of Topography and Isostatic Compensation upon 

 the Intensity of Gravity (Second Paper) ; by William Bowie. 

 Special Publication No. 12, Coast and Geodetic Survey. Wash- 

 ington, D. C. Pp. 28, pis. 5. 1912. — In the previous report on 

 the distribution of gravity over the United States 89 stations 

 were used. In the present investigation the number has been 

 raised to 124. The relation of gravity anomalies to the outcrops 

 of the several geological systems is rediscussed and also the com- 

 pleteness of compensation. It is concluded that the average 

 departure from complete compensation indicated by the gravity 

 determinations is represented by a layer of rock 630 feet thick. 

 The deflections of the vertical gave 250 feet. In neither case is 

 the result of a high grade of accuracy but both indicate a fairly 

 high degree of isostatic adjustment. Illustration No. 2 showing 

 the lines of equal anomaly is especially instructive. j. b. 



8. The Making of the Earth ; by J. W. Gregory. Pp. viii, 

 256 ; with 38 figures. New York, 1912 (Henry Holt and Co.).— 

 This is one of the volumes of the " Home University Library of 



