The results communicated to the Society were obtained from nearly five years of simultaneous observations, made twice a-day at Colinton and at the Bonally reservoir five miles south-west from Edinburgh. The height of the former station above the level of the sea is 364 feet, of the latter 1100 feet exactly; the difference 736 feet. The mean annual difference of temperature amounted to 3°.22, giving 229 feet of ascent for a diminution of temperature of 1° Fahr. The influence of the seasons is briefly shewn by the following numbers:

That the decrement of temperature is most rapid in summer, and least so in winter, has been long known.