Jan.
Cockburn Island is too feeble to melt the ice immediately beneath them; and the air was so dry during our visit, that Daniell's Hygrometer, placed hardly six inches above the ice and on the stones, indicated twenty-two degrees of difference on one occasion; and upon another, it fell from 40° to 13°, without producing any condensation. Such dryness is eminently injurious to all vegetables but lichens, which, in many cases, seem to thrive best under excessive atmospheric changes. The preponderance of the Lecanora in Cockburn Island cannot arise from this exsiccation stimulating its growth; but may be caused by the reaction that takes place afterwards, on the rapid condensation of vapour previously heated by the temperature of the rocks upon which it grows."