402 SCIENTIFIC RECORD FOR 1883. 



The United States Lake Survey. — There has just been issued by the Chief 

 of Engineers, in a quarto of 920 pages, with thirty plates, a detailed re- 

 port of the operations in the j)rosecution of the survey of the Great Lakes. 

 This important work is now finished, and the report presents in a com- 

 prehensive manner the methods used and results obtained. The report 

 starts with a historical account of the survey, from its inception in 1841 

 to its completion; gives a synopsis of the work accomplished under the 

 various officers who from time to time have had charge of the survey ; 

 gives an account of the standards of length upon which the surveys 

 depend, of the measuring-bars used and methods of using them, and of 

 the results obtained both in*the measurement of the base lines and in 

 the results of their connection by triangulation, and of the geodetic and 

 astronomical work. The part devoted to the discussion of the base ap- 

 paratus will be found of special interest to geodeticians. Full account 

 is given of the determination of the constants of the apparatus used, 

 and of the coefficients of expansion. Also, there is a discussion of the 

 " set" of a zinc bar when heated. A portion of the book is devoted to the 

 consideration of the mean levels of the Great Lakes, and the methods by 

 which the results were obtained. The question of tides in the lakes had 

 been previously considered (Report of Chief of Engineers, 1872). The 

 tides are perceptible, but of scientific rather than practical importance, 

 the maximum being less than 2 inches. — (Professional Papers, Corps of 

 Engineers, No. 24.) — (Science.) 



General movements of the soil. — Dr. Hirsch, director of the Keuchatel 

 Observatory, has published an accouut of the motions of the pillars whch 

 support his transit instrument, during the years 18G0-1882. The whole 

 series is analyzed and leads to the following conclusions : 



1st. The hill on which the observatory is situated oscillates each year 

 about the vertical. On the average it moves 39".8 each summer from 

 left to right, and 38". 2 each winter from right to left. Thus there is a 

 progressive twist, beside the periodic ones. 



2d. The hill changes its level progressively 24" yearly, and always in 

 the same direction. Thus since 1859 the change of level (towards the 

 west) has been 550". Dr. Hirsch compares the changes with the num- 

 ber of spots on the sun, and finds a connection between the two phe- 

 nomena. 



Mr. Faye,in reviewing this paper of Dr. Hirsch's, points out that the 

 phenomena can be explained by the geological structure of the strata 

 below the Jura. They are calcareous and clay beds which can slip the 

 one over the other. Water does not penetrate the layers of clay, but it 

 lubricates their surfaces and facilitates the sliding of one layer relative 

 to another. The layers of limestone are moreover filled with holes and 

 fissures running in various directions, and therefore excellent reservoirs 

 for subterranean water. Mr. Faye explains the phenomena in question 

 by supposing a stratum of limestone which is turning periodically over 



