The observations on solar radiation were made from maximum black-bulb thermometers in vacuo. The instruments used were made by J. Green, of New York. No error cards were sent with them, and it has been assumed that their readings are correct and comparable. Unfortunately the thermometers were not graduated below zero, Fahrenheit [-I7.8 deg C], and in consequence many readings were lost during March, immediately after the return of the sun.The thermometers, two in number, were mounted 2 feet [0.6 m] above the ground, one (marked S. in record) with the bulb due south, and the other (marked N.) due north. In general the instrument pointing south read the higher, but not infrequently the reverse was true.Original data in [deg F] calculated to [deg C]: [(F) - 32)] * 0.555556 = (C)