Page:Popular Science Monthly Volume 80.djvu/140

136 of a heavy dew near the Falls of the Missouri is attributed to the greater dampness of the air in that place resulting from the spray produced by the falls. This reminds one of the reported appearance of dews in the vicinity of desert oases, and of the tradition that travelers across deserts have often been assured of their approach to an oasis when they have observed that dew forms at night. The frequent firing of the grass on the Great Plains by the Indians is often referred to, but there is no reference to the possible effects of this custom upon the treelessness of the region.

The winter time which was spent by the Lewis and Clark Expedition on the Pacific coast, at the mouth of the Columbia River, gave Captain Lewis abundant opportunity to observe the meteorological and climatic peculiarities of that region, and to contrast them with those with which he had become familiar in the east. "The loss of my thermometer I most sincerely regret," he wrote on January 3, 1806. "I am confident that the climate here is much warmer than in the same parallel of latitude on the Atlantic Ocean, though how many degrees it is now out of my power to determine." A few days later we read, "Weather perfectly temperate. I never experienced a winter so warm as the present has been," and note is made of the fact that the Coast Indians wore, and needed, less clothing than those east of the mountains. Clouds, and heavy rains and gales—much changeable stormy weather and very little sunshine—made such an impression that Captain Lewis wrote, "The vicissitudes of the weather happen two, three or more times in half a day." The early part of the winter was so mild that, as already noted, it could not fail to attract attention for that reason. There being no ice, meat was smoked in order to save it, and even that method was by no means uniformly successful. Later on, however, we find frequent mention of greater cold, of snow and of "hail" (frozen rain?). On January 28, 1806, a vessel of water was exposed in order that the thickness of ice might be measured. Unfortunately, the water was only two inches deep, and it froze to the bottom. "How much more it might have frozen had the vessel been deeper is therefore out of my power to decide," was Captain Lewis's interesting and critical comment. It is clearly stated that the winds from the land were cold and clear, while those obliquely along the coast or off the ocean brought warm, damp, cloudy and rainy weather. Thus a significant climatic control received early and explicit recognition. Later in the winter (March 6) this earlier statement was qualified as follows: "Easterly winds which have heretofore given us the only fair weather we have enjoyed seem now to have lost their influence in this respect." The strongest winds came from the southwest. There is further an interesting statement to the effect that a certain harbor was not protected