AMERICAN 
JOURNAL OF SCIENCE AND ARTS, 
[THIRD SERIES] 
ART... L,— ee. is points in Mallet’s Theory of ae 2 y. by 
. W. Hiuearp, Univ. of Michig: 
[Presented to the National Academy of Sciences, April 24, 1874.] 
THE main points of Mallets Theory of Vulcanicity have 
age before the world of science for some time, and teton ex- 
of access, that few of hiss interested ‘are enubled to a appre- 
Ciate the caution and laborious conscientiousness which Mallet 
has Si So to bear on his investigation and discussion of this 
most complex problem; and to what extent he has himself 
ditivipated most of the objections raised. In calling attention 
to some apparent omissions in this respect, it may be useful to 
recall the state of the spies as regards some of the more 
prominent ot eee at issu 
The first and most omni attack upon the very basis of 
Mallet’s nie comes from Sir Wm. Thomson, in a letter to 
Mr. Poulett Scrope (Nature, nie 1, 187 2), 3 in ie ch he von 
attention to, and re-affirms, the results o 
(supplementary to that of Hophins) on the Bont ohio a fluid 
nucleus and imperfect rigidity of the earth must exert upon 
precession and nutation; and which led him to the conclusion 
sas, unless the rigidity of the globe as a whole were greater 
than that of steel, there must ensue a tidal deformation of the 
solid mass, which would sensibly change the amount of preces- 
AM. Jour. 8ot.—Tiinp Sete, Vou. VII, No. 42.—June, 1874, fae dik 
