94 Williamson , — Some Experiments on the Action of 
Sample II. Scotch Pine. 
Condition. 
Weight 
in grm. 
Dry wt. 
Mois- 
ture 
%• 
Temp, of 
Exposure. 
Time of 
Exposure. 
Spring 
Wood. 
Autumn 
Wood. 
Condition 
of 
Negative. 
la. 
Air dry 
3 I -485 
27.860 
13.0 
4 o°C. 
24 hrs. 
+ ? 
— 2 
Very faint 
b. 
Moist air 
35-035 
25-7 
j 1 
+ 
— 
More dense 
3 days 
than 1 a 
2 a. 
Dried over 
31-549 
28.880 
9.1 
5 ) 
+ 
— 
Fair 
h 2 so 4 
b. 
Moist air 
34.760 
20.3 
>> 
>> 
+ ? 
_ ? 
Faint 
3 days 
3 a. 
Dried over 
30.499 
27-565 
10.68 
JJ 
iy 
+ 
— 
Good 
CaCl 2 
b. 
Moist air 
32-335 
17-35 
+ 
— 
„ (a little 
3 days 
clearer) 
4 a. 
Dried at 
29.279 
JJ 
>> 
+ 
— 
Better than 
ioo° C. 
any 
b. 
Moist air 
33 - 19 ° 
13-35 
>> 
+ 
— 
As good as 
3 days 
4 a 
The results from the Oak used were on the same lines as these. It is 
obvious from these results that the amount of moisture present seems to 
affect the kind of negative produced very little, if at all. The negative 
obtained from wood that has been dried at ioo° C. and that from the same 
piece of wood containing 13*35 per cent, of moisture are indistinguishable. 
In each case the negative obtained from an air-dried piece of wood, ex- 
posed at a given temperature and for a given time, is fainter than where the 1 
wood has been dried over calcium chloride or at a temperature of ioo°C. 
This difference is hardly stable or marked enough to use it as a criterion 
for determining the exact temperature used to season a given timber or the 
amount of moisture present in a given timber. 
Images were obtained from kiln-dried Scotch Pine and Oak by this 
method, and they agreed in every detail with the negatives obtained from 
air-dried specimens which had been left in moist air for three days. The 
only difference observable in some of the samples was that wood, dry 
heated to ioo° C., often gave a denser image with a shorter exposure than 
was the case with the unheated samples, but the character of the image was j 
the same. Dry heating to ioo° C. may be said to increase the activity of 
the wood. 
The effect of heating the wood in steam was observed. Thin pieces of 
four samples of Scotch Pine were subjected to steam for twelve hours. 
Images were then obtained in the dark. Three of the samples made no 
impression on the plates after an exposure at 40° C. for forty-eight hours. 
The fourth gave a fair negative, but rather poor in intensity. A longer ex- 
posure was tried with the same result. The steaming had evidently 
inhibited the activity of the wood ; controls showed activity in all four 
cases. After forty-one days images of the samples were again taken. 
