[M’LEOoD & BARNES] NOTES ON THE DIFFERENCE OF TEMPERATURE 5 
Royal. The difference in altitude between Reno and the summit of 
Mount Rose is 6,268 feet, as contrasted to the difference of altitude of 
our stations, which it may be remembered is 630 feet. Nevertheless, 
the work, so ably carried out by Prof. Church in the face of so many 
difficulties, possesses features which particularly bear on the problem 
before us, and these are the frequent observations of advance changes 
both as regards temperature and general weather conditions. Prof. 
Church has compared the thermograph records obtained on the summit 
with similar records obtained at Reno, and finds advance times of warn- 
ing for temperature changes. Thus at noon on May 14th a period of 
low temperature set in on the mountain top thirty-six hours before the 
first appearance of frost in the adjacent valley. In general the time 
interval of warning for a temperature depression on Mount Rose to 
reach the region below at Reno is placed at from twenty-four to thirty- 
six hours. Our time intervals of warning are less than this, which 
is, no doubt, due to the great difference in altitude of the respective 
stations. 
In a recent letter which we have received from Prof. Church, he 
states that he has a ready means of frost-forecasting in April and May, 
derived from last season’s observations. He finds that as Mount Rose 
is so high that disturbances there are visible at Reno through the con- 
densation of vapour into cloud about the summit. The result of this 
is a slight disturbance at Reno the same or succeeding day which ends 
in frost if the night is clear and calm. Prof. Church further cites an 
example of his method of forecasting general weather conditions. He 
states that on one evening when he observed a dull sky over the summit 
that rain fell the following night, but a clear sky over the summit and 
calm air, colder conditions with frost followed. 
A plan has been formed by Prof. Church for placing several 
observatories at different altitudes within reach of Reno in order to 
observe along the path of the general current from west to east. He 
considers that the storm movements and storm settling could be roughly 
estimated by this means. It is to be hoped that Prof. Church will 
succeed in this plan, for we have little doubt but that he will obtain 
meteorological data of the greatest importance. 
We now desire to present for consideration an analysis of our 
entire series of observations from the first, including the very excellent 
series which we have obtained during the past year. 
In the accompanying table we give the mean monthly difference 
between the Observatory and Mount Royal, for each month during 
which it was possible for us to obtain traces. 
