70 DIFEICULTY OF DRYING PLANTS. ch. hi. 



Nothing is more common with us at home than to grum- 

 ble at the dampness of the climate ; and, as far as the 

 effects on the human animal are concerned, our complaints 

 are perfectly just. Air at 50° Fahr. cannot at the utmost 

 carry more than about 4^ grains of aqueous vapour to the 

 cubic foot ; but at that temperature it produces, when 

 nearly saturated, that feeling on the nerves of the skin, 

 familiar to every inhabitant of these islands, which is the 

 ordinary forerunner of colds, sore throats, rheuniatism, and 

 many another ailment. But the botanist, to whom the 

 condition of his drying paper is even more important than 

 that of his own body, finds an easy remedy for the incon- 

 venience. By exposing his damp paper to a temperature 

 of from 80° to 90° in the sunshine, or before a fire, he 

 readily obtains a satisfactory degree of relative - dryness, 

 and in a very few days his specimens are in a state to put 

 away, and with ordinary care need give him no further 

 trouble. But the case is very different where the ordinary 

 temperature of the air in the shade is about 75°, as was 

 the case here, not to speak of 85° which is the common 

 limit in the tropics. To the human body there is nothing 

 unpleasant in the effects of such air when nearly saturated 

 with vapour, and so long as the temperature remains 

 habitually between 70° and 80° it is decidedly favourable 

 to health, if not to vigorous exertion. But a cubic foot 

 of air at 77° contains nearly 10^ grains of vapour, and 

 when at all near to the point of saturation it has no 

 perceptible drying effect on surrounding objects, and a 

 moderate increase of 10° or 12° Fahr. in temperature has 

 but a slight effect in increasing its desiccating power. 

 We were first struck by remarking the very long time 

 required to dry the decks as compared with what is usual 

 in the Mediterranean, and we had still more painful 

 experience of the difficulty of drying our paper. We 

 were now the sole occupants of the saloon, and our captain 

 left us free to use every part of the steamer ; the deck was 

 soon turned to account, cords were stretched across the 



