METEOROLOGY OF i8q7 
9 
put into Fahrenheit degrees by multiplying the reading in 
centigrade by i.8 and adding 32°. By means of a special 
series of observations, indications of this instrument may 
be interpreted and expressed in calories, or units of heat. 
§36. To say that the heat received is one calorie, is to 
say that the heat received on one square meter is sufficient 
to heat one kilogram of water one degree C. in one minute. 
§37. The enormous force contained in the sunshine is 
not generally realized. If we express this in horse power 
per square yard, 10 calories is equivalent to nearly 8-10 
(.82) of a horse power per square yard, or when the radia- 
tion amounts to as much as 12.8 calories, the solar energy 
which is being received, is equivalent to on(i horse power 
per square yard. An examination of the column shows that 
this often exceeds one horse power per square yard of sur- 
face perpendicular to the sun’s rays. 
§38. These observations have been carried on now for 
a number of years at this institution. They are the first, so 
far as is known, in this country. The instrument is read at 
noon on week days, d'he numerous blanks are due to the 
absence of the observer at outside observations. 
§ 3Q. The column of frost or dew indicates the dates 
on which the frost or dew was observed. It does not denote 
that these were the only days. During the summer, it is 
probable that many days of dew have been overlooked, for 
the dew has time to evaporate before the observation at 7 
o’clock is made. On nearly every morning, the reading of 
the terrestrial thermometer is lower than the dew point at 
the same time. If so, it may be certain that there has been 
dew or frost. If the radiation thermometer has been below 
32°, it is frost; if above, dew. A comparison of the terres- 
trial radiation column and the dew point temperatures at 7 
a. m. of the same day show a few such cases. 
d'he summaries in tables 2, 3, and 4, show the nuniber 
of davs during the year on which frost occurs. The greater 
amount of moisture at Fort Collins over Cheyenne Wells is 
shown by the greater number . of times that frost and dew 
were observed. 
Table 5 gives the precipitation as observed at the Agri- 
cultural College by months. As before stated, the records 
previous to 1887 were scattered and lost, although the 
observations were taken for most of the months. The 
average of the different months is used as the normal pre- 
cipitation, making the normal for the year 13.86 inches. It 
will be noticed, that during the last eleven years, six years 
have been above the normal, and one very much below. 
