Opinions of the Press on the “International Scientific Series.” 
VII 
The Conservation of Energy. 
By BALFOUR STEWART, LL. D., F. R.S. 
With an Appendix treating of the Vital and Mental Applications of the Doctrine. 
1 vol., 12mo. Cloth. Price, $1.50. 
“ The author has succeeded in presenting the facts in a clear and satisfactory manner, 
using simple language and copious illustration in the presentation of facts and prin- 
ciples, confining himself, however, to the physical aspect of the subject. In the Ap- 
pendix the operation of the principles in the spheres of life and mind is supplied by 
the essays of Professors Le Conte and Bain.” —Ohio Farmer. 
“ Prof. Stewart is one of the best known teachers in Owens College in Manchester. 
“The volume of THE INTERNATIONAL SCIENTIFIC SERIES now before us is an ex- 
cellent illustration of the true method of teaching, and will well compare with Prof. 
Tyndali’s charming little book in the same series on ‘ Forms of Water,” with illustra- 
tions enough to make clear, but not to conceal his thoughts, in a style simple and 
brief.” — Christian Register, Boston. 
“The writer has wonderful ability to compress much information into a few words. 
It is a rich treat to read such a book as this, when there is so much beauty and force 
combined with such simplicity. —Zastern Press. 
VIII. 
Animal Locomotion; 
Or, WALKING, SWIMMING, AND FLYING. 
With a Dissertation on Aéronautics. 
By J. BELL PETTIGREW, M.D., F.R.5., F.R.S.E., 
F.R.C. P.E. 
1vol.,12mo. . . . . . Price, $1.75. 
“This work is more than a contribution to the stock of entertaining knowledge, 
though, if it only pleased, that would be sufficient excuse for its publication. But Dr. 
Pettigrew has given his time to these investigations with the ultimate purpose of solv- 
ing the difficult problem of Aéronautics. To this he devotes the last fifty pages of his 
book. Dr. Pettigrew is confident that man will yet conquer the domain of the air.”— 
N.Y. Fournal of Comneerce. 
“Most persons claim to know how to walk, but few could explain the mechanical 
principles involved in this most ordinary transaction, and will be surprised that the 
movements of bipeds and quadrupeds, the darting and rushing motion of fish, and the 
erratic flight of the denizens of the air, are not only anologous, but can be reduced to 
similar formula. The work is profusely illustrated, and, without reference to the theory 
it is designed to expound, will be regarded as a valuable addition to natural history.” 
—Omaha Republic. 
D. APPLETON & CO., PUBLISHERS, 549 & 551 Broadway, N.Y, 
