250 Notices of Books. [April, 



is subjected, this crust must crush, " to follow down after the 

 shrinking nucleus It must crush unequally, both re- 

 garded superficially and as to depth ; and the crushing will not 

 be absolutely constant and uniform anywhere or at any time, or 

 at any of those places of weakness to which it will be principally 

 confined, but will be more or less irregular, quasi-periodic, or 

 paroxysmal ; as is, indeed, the way in which all known material 

 substances (more or less rigid) give way to a slow but constantly 

 increasing steady pressure." 



Such is a brief sketch of the general views of Mallet ; but for 

 the details, and particularly for the estimates of the rate at 

 which the vulcanic processes now in progress are taking place, 

 and an account of the experiments conducted to obtain these 

 estimates, the reader is referred to the present work. 



It is hardly necessary to point out how much the interest of 

 Palmieri's narrative is enhanced by its association in this 

 treatise with Mr. Mallet's inquiries into the phenomena of the 

 earth's crust. In fact, Mr. Mallet has specially tested his views 

 by a study of the phenomena presented during the last two 

 thousand years by Vesuvius, "the best known volcano in the 

 world." 



Nevertheless, it is to be noted that Palmieri's Memoir con- 

 tains much which does not bear directly on Vulcanology. It 

 will be none the less interesting on this score, however, to the 

 general reader ; and we recommend all those who are desirous to 

 learn all the circumstances of a great and characteristic eruption 

 of Vesuvius, to turn to the pages of this book. As Mr. Mallet 

 well remarks, " a special narration such as this should not 

 suffer in popular estimation by the fact that Prof. J. Phillips 

 has so recently given to the world the best general account of 

 Vesuvius in its historical and some of its scientific aspects 

 which has yet appeared." 



Papers relating to the Transit of Venus in 1874. Prepared 

 under the Direction of the Commission Authorised by 

 Congress. Published by Authority of the Hon. Secretary 

 of the Navy. Part I. Washington. 



These papers consist of a series of letters on the subject, the 

 most important being those from Mr. Rutherford, and of an 

 essay " On the Application of Photography to the Observation 

 of the Transits of Venus," by Professor Newcomb. Mr. Ruther- 

 ford describes his method for photographing the sun as a guide 

 to the method of photographing the phenomena of the transit ; 

 and then says — " If the whole matter of ordering instruments 

 for the photographing of the transit of Venus were in my 

 control, with my present lights, I should have an achromatic 

 objective of five inches aperture, and seventy inches focus, in a 

 cell which would allow of the application, in front of it, of a lens 



