860 REVIEWS 
The chemistry of brick-earths and the methods to be pursued in 
analyzing them are considered at much length. The micro-structure 
of bricks is presented in a manner to be of much aid to the practical 
brickmaker who is anxious to determine the texture of his product. 
The important question of the durability of bricks is also discussed. 
Among the tests which are mentioned by the author are the chemical 
composition of the brick, its absorptive capacity, its minute structure, 
its specific gravity, and its strength. Each of these subjects is dis- 
cussed in some detail. 
This information cannot but be highly beneficial to the brick- 
maker capable of appreciating the bearing which accurate scientific 
knowledge has upon his industry. Similar treatises to that of Profes- 
sor Harris, with American illustrations, would be of much value to 
our own economic interests. The more our operators, whether in clay 
or other mineral products, come to realize their dependence upon 
scientific fact, and they will only realize it by the geologist interesting 
himself in their work, the better for the success of their endeavors, and 
the greater influence the scientific expert will have among practical 
men generally. Wm. B. CLarK. 
