96 BOTANICAL GAZETTE [FEBRUARY 
Working with only 200 cc. of water, at the most, I have never been 
able to pour this water from the flask in which it was heated into 
the Dewar flask so quickly that no heat was lost. I used a thin- 
walled round flask for heating the measured quantity of water; I 
cut the neck of the flask to a length of 2 cm.; while being heated 
the flask was held by a small wooden test abe holder of the usual 
form; the thermometer for determining the temperature of the 
water remained with its bulb under water in the flask while it was 
heated; and I took pains not to let the flask touch anything after 
taking it from the flame, until it was emptied. By holding the 
flask with the wooden holder while the water in it was warming, 
I warmed the holder, and as wood is a non-conductor, I felt that I 
was taking the least possible heat from the water myself in pouring 
it. In these and in other ways, therefore, I have taken such pains 
as I could to reduce the inevitable error to its lowest terms; but 
the error in calorimetry is stated by LutHER-OsTWALD to be about 
I per cent under the most favorable conditions, and with larger 
volumes of liquid than I have so far been able to use. A typical 
series of figures follows, with the averages of a considerable number 
of determinations for four calorimeters. 
April 2, r9t0 No. 11-5 No, 12-2 | No. 14-6 | No. 8-8 
Lenten, Oy. sc ees 27.6° 29. 2° 29.1° | 28.7° 
21 itr 3 ef se trae Gomera ea 45.0 42.0* 42.0 40. 
BOCOMIOd: Cocina eels 43.2 40.75 40.5 38.55 
Mees ct ts cageees .y 1.8 t. 5 I 
Calories lost... .. Urs G 360.0 247.0 bP 300.6 | 290.0 
Gain taaupaciture Se ee 15.6 PERS 4 ee | 8 
Calories per degree........ 23.07 | 21.4 | 26.3 20.4 
* Measured 197 cc. 
The averages for four calorimeters follow: 
No. 11-5, 15 ee avereee ea : a — , 
No. 12-2, 15 cc 
No. 14-6, Io cc ce 24. : iad “ “ce 
No. 8-8, 13 mS tae bie il 
The average of these four calorimeters is 25.6 calories per Centi- 
grade degree. This means that the average calorimeter, consisting 
of a silvered Dewar flask of 250 cc. capacity made by Burger of 
Berlin, a long thermometer graduated to tenths of a degree, and a 
cotton plug suitable to close the neck of the flask, required a quan- 
