28 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



cated between the volcanic emanations and the metalliferous 

 strata that have been introduced (injected?) into the crust 

 of the earth. The presence of boric acid, now established 

 among the products of Vesuvius, bears directly on the con- 

 nection already suspected between the volcanoes of Central 

 Italy and the hot springs of Tuscany, the products of which 

 latter, concentrated in the lagoons, form one of the principal 

 deposits of borax at present resorted to for that article. 6 

 i?, 1873, 361. 



ROTATION OF THE EARTH ON ITS AXIS. 



It is tvell known that the astonishing accuracy attained by 

 Struve in his observations with the jDrime vertical transit, 

 and the remarkable agreement of the results obtained by 

 him in his determination with it of the so-called constant 

 of aberration, led him to hope for a similarly happy result in 

 the application of the same astronomical instrument to the 

 determination of the nutation. Struve contemplated the fre- 

 quent observation of three well-selected stars during a space 

 of nineteen years, in order to follow the nutation of the 

 earth's axis through all its changes. His death, indeed, pre- 

 vented the perfect accomplishment of this tedious work ; but 

 the observations that he did make run through a period of 

 fifteen years, and have been supplemented by those of the 

 other astronomers at the Imperial Observatory of Russia, so 

 that the nutation has lately been deduced from these ob- 

 servations, with all desirable accuracy, by Dr. M. Nyren. 

 "Without doubt," says Dr. Nyren, "we have here the most 

 accurate series of observations of so great an extent that- as 

 yet exists." The probable error of a single determination of 

 the zenith distance of a star amounts to but 0.1". The ac- 

 curacy of this long series of observations has led Nyren to 

 not only develop anew the mathematical principles respect- 

 ing the movements of the earth's axis in space, in which he 

 introduces such slisfht refinements as have been su2ro:ested 

 by the progress of science since the appearance of the classic- 

 al works of Dr. C. A. F. Peters, but also to attempt a solu- 

 tion of a problem first proposed by Euler, who demonstrated 

 that if the earth's axis of rotation does not correspond to the 

 axis of greatest moment of inertia, then it will not be fixed in 

 reference to the earth's solid bodv, but will describe a small 



