174 The American Geologist. Manh, 1905 
the water charged with lime from flowing through a lime- 
stone formation, would naturally leave a chalky deposit. 
More than 130 feet above the present level of the town wc 
find this deposit lying in thick beds, and also underlying 
the city at a depth below the surface of from one to ten 
feet, with a thickness of from 30 to 40 feet. 
Till within the last ten years this deposit of soft lime- 
stone, called "sillar," which has the color and consistency 
of chalk and lies in horizontal beds, has been the only 
building material in use in the city of Monterey, and it is 
still emplo^-ed for nearly all common buildings on account 
of its cheapness and many excellent qualities. It loses its 
coherence when subjected to a temperature below the 
freezing point. 
Underneath this formation is found a bed of coarse 
gravel mixed with large boulders through which an abund- 
ance of fresh water flows. The depth of this gravel bed 
has never been ascertained. The present water supply of 
the city comes from wells sunk down to this formation. In 
these wells the water shows a tendency to flow from south- 
west to northeast. In some the flow is clearly visible. 
As we do not know how much of the sillar deposit has 
been carried away in solution, or how the tem])erature and 
climatic conditions may have changed since the time of its 
formation, it is impossible to make an exact estimate of 
the time recpiired to lay down the vast beds which now 
exist. Granting that the conditions were the same, or 
nearly the same as they are to-day, we may assume the 
evaporation from the surface of the former lake to have 
been about three sixteenths of an inch in 24 hours, or 
about 6 cubic feet per square foot of surface, per year. The 
evaporated water may have contained 0.385 parts of prim- 
ary calcium carbonate in 1000 parts of water, or 0.24 of 
secondary carbonate of lime at a temperature of 59° Fahr. 
An analysis recently made ])y Mr. Butsch. chemist of the 
Monterey steel works, resulted in 0.23 parts carbonate of 
lime in 1000 parts of water. 
The former temperature may have been higher than 
59°. so we may assume 0.25 parts in loco parts. This would 
give a yearly precipitation of 0.0015 ft. or 15 feet in 10,000 
