CHAP. III - TERM-DAY WORK

Summary

The method of “term,” or stated days, whereon meteorologists should observe throughout all the twenty-four hours, was an improvement introduced by Sir John Herschel, when studying the climate of South Africa. So admirably is it adapted to bring to light phenomena of short period, that I was happy when the morning of July 21st arriving, enabled me, with a semblance at least of utility, to begin the hourly observations of that particular term-day. At six o'clock, accordingly, the first entry of the series was made.

Our meteorological observatory was now pretty satisfactory as to arrangement, and was practically efficient in guarding against local disturbances. These were mainly two; first, the terrific radiation of the sun by day, with something of the same sort, but with an opposite sign, from the sky by night; and, secondly, the wind, which, if allowed its own sweet will, might at any moment blow all our instruments into the crater. To protect from these, a portion of a room had been erected, with walls to the S.E. and W., and with a bit of roof formed of planks and canvas, covered in with brushwood and weighted with rock. This roof was to keep out the almighty prying of a vertical mountain sun, whose rays did indeed try the nature of everything they had access to. The walls were of stone, and pretty nearly four feet thick, so that there was no fear of direct solar radiation getting through them.