CLIMATE IN THE CURE OF CONSUMPTION. 425 
percentage of saturation of the air, would be sufficiently accurate as a basis of 
comparison, yet, as it might be objected that such a table would be subject to 
error, we have appended another table, giving the absolute moisture, or the 
number of grains of vapor to the cubic foot of air. This second table we have 
computed from Glaisher's Tables. ^ 
Consulting these tables it is seen that Denver and Santa Fe afford a very 
low relative and absolute amount of atmospheric moisture, — a relative amount, 
which, as between Denver and Jacksonville, is as i to 3, and, as between Denver 
and Los Angeles, is as i to 2 . 
This proves, that, on the eastern slopes of the Rocky Mountains, we have, 
in addition to the favorable element of elevation, a second, that of dry air, as an 
element of climatic influence in the cure of phthisis. 
Precipitation. — Closely related to the foregoing, is a consideration of the 
mean annual precipitation, or the mean annual amount (in inches) of rain and 
melted snow. Its bearing on our subject is apparent in several ways, 
1. Of the precipitation, a certain part is lost by evaporation, and tends to 
increase the humidityof the air. This amount will depend upon the amount of 
moisture in the air, or its degree of saturation, and also upon the amount of the 
precipitation left upon the surface of the ground to be evaporated. It is evident 
that the greater the porosity of the soil, the greater will be its absorptive power, 
and the less the evaporation from it. Such a porous soil is found on the eastern 
slopes of the Rocky Mountains. Loose, sandy, and gravelly, it eagerly drinks 
up all the rainfall; and such a thing as mud is rarely seen. 
2. It is well known that pulmonary troubles are most prevalent during 
"thaws," in those places where the snow lies upon the ground in winter. Now, 
in the district of the Rocky Mountains under consideration, there is, in the first 
place, only a slight amount of snowfall, so that sleighing is exceptional, and, in 
addition, the warm sun soon melts the snow, and the thirsty, porous soil drinks 
it up; so that the annual "spring thaw " of our Eastern States is a res incognita 
in this country. The writer remembers very distinctly several snowfalls of four- 
teen to twenty-two inches on a level, of which there was not a vestige left in ten 
days; and during that time the air was not chill and raw, and there was but little 
slush. 
3. Further than this, the amount of the precipitation has a bearing upon 
our subject, as indicating approximately the ability of the invalid to lead an out- 
of-door life. We shall defer our discussion of this point to a later part of this 
paper. 
Turning now to the tables we see that in Denver the mean annual precipita- 
tion for a period often years is only 14.77 inches in rain and melted snow,— an 
amount which is only one-fourth of that at Jacksonville, and which, with Santa 
Fe, gives the smallest showing in our range. 
We can, therefore, add this element of climate to the other two of elevation 
and dry air as a point in favor of the Rocky Mountains in the cure of phthisis. 
1 Omitted. 
