1912] PEIRCE—RESPIRATION oI 
two days later, April 2, a temperature of 16.50° C. The highest 
maximum came at some time aariNg my absence in the summer 
vacation, a temperature of 20.55° C., which, however, differed from 
the temperature at the time I made and recorded the observation on 
August 13 by only 0.05°. The highest minimum was in mid May. 
Between the highest and lowest maxima there was a difference of 
3.5°; between the highest and lowest minima a difference of 1.55°; 
and between highest maximum and lowest minimum a difference of 
4.05° from late March to mid August, with an average daily range 
of o.71° on 13 days in March, April, and May. It is needless to 
say that these chambers might be warmed, and presumably their 
temperatures would be very nearly as constant, but in this mild 
climate, in which there is little frost even at night in midwinter, 
and still less excessive heat in midsummer, artificial heat seems 
unnecessary, at least for experiments on the respiration of such 
germinating seeds as peas. | 
Having thus established the remarkable constancy in the tem- 
perature of these chambers, I may now pass to a consideration of 
the apparatus employed. I have used silvered Dewar flasks made 
by Burger of Berlin and imported “duty free.” These Burger- 
Dewar flasks are stamped and numbered by the maker. Their 
efficiency is very uniform. Experience with the unsigned flasks of 
other makers quickly shows that they are not so uniformly efficient 
as they should be. For the sake of convenience and economy, not 
at first realizing my mistake, I have continued to use flasks of about 
250 cc. capacity. But I am sure that flasks of not less than double 
this capacity would be more satisfactory because involving smaller 
physical errors.4 Most of the flasks are simply double-walled 
round-bottom flasks, like fig. 1, but I have had four made in which, 
as indicated by fig. 2, the interior drains through a tube opening 
at a. This opening is small, but it seems to be sufficient to carry 
off carbon dioxide as well as water. At the same time, it does not 
greatly reduce the efficiency as an insulator of a well-made flask, 
and does add materially to its convenient use, making it possible to 
4See Ostwap-LuTHER, Physikalisch-chemische Messungen 2: Pi — — 
BERTHELOT’s results are cited as indicating t 
of less than half-liter capacity. 
£ 
