cd 
IN A SATURATED ATMOSPHERE. 307 
Weight in 
Misi es. Loss per cent. | Temp. (W. & D.). 
o 
May 9th. 18:005 
» 10th. 17-980 ‘025 56 
» lith. 17:940 034 675 
„ 12th. | 17:930 ‘016 ? 
» 18th. | 17:890 040 59 
» 14th. | 17'855 035 59 
» lh. | 17-840 015 63 
» 16th. | 17'785 055 65 
» J7th. | 17713 072 62 
» 18h. | 1770 008 59 
The total loss was therefore ‘390 gramme, and the mean loss 
per day :035 gramme. 
These two cases, several times repeated and corroborated by 
others which I need not quote, fully prove that dead saturated 
substances continue to evaporate, notwithstanding that the atmo- 
sphere in which they are suspended is apparently saturated ; we 
can only conclude with Knop that it is impossible to maintain 
the air saturated with vapour. 
Since the temperatures within the jar are constantly changing, 
the capacity of absorption must vary accordingly, and when the 
temperature rises, ove can understand that the air can absorb 
more vapour, and may extract it from the substance or leaf ex- 
perimented with as well as from the water at the bottom of the 
jar. But when the temperature falls, it is not so easy to see 
why cotton-wool or a sponge should still lose moisture. Such, 
however, is evidently the case. 
A point to notice in these experiments is that while living 
specimens gained weight at night, dead substances never did so, 
but Jost weight under all circumstances. Thus, when the glass 
jar was entirely excluded from light, and a piece of cotton-wool 
saturated with distilled water, weighing 8'670 grammes, was 
suspended within it for seven days, it lost ‘165 gramme, or 
‘022 gr. per day. It would seem, therefore, that the power to 
absorb the vapour of water must be regarded as a property of 
living protoplasm, since dead cellular tissue (as cotton-wool) 
entirely failed to do so; and tbis furnishes an additional differ- 
ence between living and dead organic structures. 
Saad n. 
