506 Notices of Books. [October, 
‘‘§ There are three general measures :— 
‘¢1, Space is measured by the straight line, and its compounds 
represented by the respective measuring instruments. 
‘‘2. Matter is measured by weight. 
‘3. Force, or its intensity of action, manifesting itself as ve- 
locity, is measured by the diurnal rotation of the earth, 
the day and its divisions, represented by time-pieces. 
‘““§ Every language contains words which designate space, 
matter, and force. 
‘‘The mathematical formule of physics, pre-eminently the 
science of motion, contain the signs of these elements.” 
The book cannot be merely read; it must be studied line by 
line, word by word, and is well worthy the trouble. 
Treatise on the Manner of Testing Water-Wheels and Machinery. 
By James Emerson, of Lowell, Mass. Lowell, Mass.: 
Stone and Huse. 1872. 
WHILE we cannot here enter into a description of the methods 
of testing water-wheels and machinery employed by Mr. Emer- 
son, his eminence as an American engineer will recommend his 
work to the notice of all concerned in this branch of engineering 
construction. ‘The book is fully illustrated with engravings of 
the various wheels and turbines in use in American streams; 
and contains tables of quantities of water, in cubic feet per 
minute, flowing over weirs of different lengths, with varying 
depths of water, as well as tables of the velocity due to head of 
water. ‘The work contains much in little space. 
Corso di Geologia del Professore Antonio Stoppani. Volume I. 
Dinamica Terrestre. Milano: G. Bernardoni e G. Brigola. 
EO7 1. 
Tus course of geological study is virtually an enlarged edition 
of the ‘‘ Note ad un Corso di Geologia,” published by Professor 
Stoppani in 1865. ‘The present work will be comprised in three 
large octavo volumes, of which the first is now offered to the 
public. The subject of terrestrial dynamics is considered under 
two heads—the dynamics of the exterior of the earth, atmo- 
spheric and oceanic circulation, &c., and the investigation of the 
action and results of subterranean forces. Under the latter head 
we have a full but concise account of volcanic eruptions, parti- 
cularly of the history of Vesuvius. The work is well illustrated, 
and will form a valuable addition to the library of the geologist, 
as being a record of geological facts founded upon the authority 
of Dr. Stoppani. 
