Geography of the Air. 53 
lost consciousness. The man states that he felt no shock, but 
was suddenly enveloped in light and that a ball of fire the 
size of his fist, traveled along the horse’s neck. This points to 
the fact that “ball” lightning is probably a physiological phe- 
nomenon. 
In view of the recent extended interest in the question as to 
whether the climate of the United States is permanently changing, 
it should be remarked that this question has lately been under con- 
sideration with regard to Europe. Messrs. Ferrel, Richter, Lang, 
Bruchen and others conclude, from an examination of all avail- 
able data, that there is no permanent climatic change in Europe. 
In connection with this discussion in Europe, long series of 
vintage records, going back to the year 1400, have been used. 
Apart from the ocean borders, extensive simultaneous climatic 
changes occur over extended areas, which changes—as might be 
expected—are more accentuated in the interior of the continents. 
_ These changes involve barometric pressure, rainfall and tempera- 
ture, which all recur to that indefinite and complex phenomenon— 
the variation in the amount of heat received by the earth. Theidea 
is advanced that these oscillations have somewhat the semblance 
of cycles, the period of which is thirty-six years. It may easily 
be questioned, however, in view of the fragmentary and hetero- 
geneous character of the data on which this assumption is based, 
whether the, error in the observations is not greater than the 
range of variation. Blanford, in one of his discussions, has 
pointed out that the temperature or rainfall data in India can be 
so arranged as to give a cycle with a period of almost any num- 
ber of years, but, unfortunately, the possible error of observation 
is greater in value than the variations. 
As to the United States, it is pertinent to remark that the 
Signal Office is in possession of temperature observations in 
Philadelphia, covering a continuous: period of one hundred and 
thirty-two years. The mean annual temperature for the past ten 
years is exactly the same as for the entire period. 
There have been criticisms in years past that the climatological 
conditions of the United States have not received that care and 
attention which their importance demanded. Much has been 
done to remedy defects in this respect, although, as is well known 
here in Washington, the general law which forbids the printing 
of any works without the direct authority of Congress, has been 
an obvious bar to great activity on the part of the Signal Office. 
