THE CAVE-DWELLERS OF THE SAN FRANCISCO MOUNTAINS. 273; 
The second coat, called surface-coat, prepared as above specified, shall be laid 
on the cushion-coat ; it shall be brought to the ground in carts-, at a temperature 
of about 250° F., and if the temperature of the air is less than 50°, iron carts- 
with heating apparatus shall be used in order to maintain the proper temperature 
of the mixture, it shall then be carefully spread, by means of hot iron rakes, in 
such manner as to give a uniform and regular grade, and to such depth that after 
having received its ultimate compression, it shall have a thickness of two inches. 
The surface shall then be compressed by hand rollers ; after which a small amount 
of hydraulic cement shall be swept over it, and it shall then be thoroughly com- 
pressed by a steam roller, weighing not less than 250 pounds to the inch-run, the 
rolling being continued for not less than five hours for every 1,000 yards of sur- 
face. 
The powdered carbonate of lime shall be of such degree of fineness that 5 to 
15 per cent by weight of the entire mixture for the pavement shall be an impalp- 
able powder of limestone, and the whole of it shall pass a Noi. 26 screen. The 
sand shall be of such size that none of it shall pass a No. 80 screen, and the 
whole of it shall pass a No. 10 screen. In order to make the gutters, which are 
consolidated but little by traffic, entirely impervious to water, a width of twelve 
inches next the curb shall be coated with hot pure asphalt and smoothed with hot 
smoothing irons, in order to saturate the pavement to a certain depth with an, 
excess of asphalt. 
ANTHROPOLOGY. 
THE CAVE-DWELLERS OF THE SAN FRANCISCO) MOUNTAINS. 
GENERAL M. T. THOMAS. 
A considerable number of these ancient dwellings are found in the vicinity of 
Flagstaff, and at one point, about eight miles northwest of that station, a village 
of fifty or more caves is still in a fair state of preservation. 
This village is located on the point of a sharp ridge of land rising quite 
abruptly above the ordinary level of the mountain range about 500 feet. It is 
not by any means upon the highest part of the ridge, neither could it have been 
selected as a defensible position, but principally on account of the character of 
the material in which the caves have been excavated. 
This material is partly lava scoria, an occasional solid lava rock, the whole, 
substance being partially cemented by heat with earthy substances sufficiently 
compact to render the roof and wall of the caves safe and permanent. 
The caves in this particular village cover a space about 200 feet along the 
