380 Miscelianies. 
ciently full in detail, and well composed. He considers first the calca- 
reous minerals, and the limes which they furnish. Next, the various 
materials employed in the preparation of mortars—in this chapter un- 
der the head of sand, he says, (p. 25, Art. 53,) ‘‘ sand performs no 
chemical part in mortars, but is entirely passive in its influences,” &c. 
This seems to us too broad an assertion, as it is by no means certain that 
caustic lime does not form a combination with the silica of fine sand in 
mortar, and this circumstance (the formation of an insoluble silicate) may 
exert an influence in the final consolidation of calcareous cements. 
This does not interfere with the generally accepted opinion, that mor- 
tars owe their chief consistency to the gradual conversion of the lime 
into carbonate. 
The general composition of mortars and their resistance ; the fabri- 
cation of limes in the large way; the preparation and application of 
various kinds of mortars; concrete and some of its applications, and 
the theory of the solidification of mortars—are made the subjects of 
distinct chapters, all of which contain interesting and important infor- 
mation ; but the last, especially, commends itself to the attention of 
Chietiiists: as embracing some curious and valuable results obtained by 
Lt. Kendrick of the artillery, and Assistant Professor of chemistry at 
West Point Military Academy. These researches had for their object 
to determine the cause or causes of the hydraulic powers of certain 
cements—a question which has had many proposed solutions. Berg- 
man and Guyton de Morveau, who were the first to investigate this 
subject, attributed the hydraulic power to the presence of a minute 
quantity of oxide of manganese in the limestones from which the spe- 
cimens examined by them were obtained. 
‘Mr. Smeaton, an English engineer, had remarked however as early 
as 1756, the curious fact, that the existence of clay in a calcareous 
stone, gave it the property of indurating under water; and Saussure 
discovered that the lime of Chamouni, though entirely without manga- 
nese, was nevertheless hydraulic, and with reason inferred, that this 
property depended on the clay which existed in the lime. Subsequent 
researches confirmed this opinion. In 1817, M. Vicat (a well known 
writer on cements) formed hydraulic cements synthetically, by cal- 
cining mixtures of common lime and clay. His experiments proved 
that clay imparted hydraulic properties to lime, and manufactories 
were established for making water cements by the mixture of the two 
substances. 
In Lt. Kendrick’s experiments the pure ingredients of each compo- 
sition were thoroughly mixed by the mortar and pestle, and in the pro- 
portions stated in table. If lime or magnesia was used, it was 
previously slacked with hot water; if the carbonate of either was em- 
