93 
Wood on Photographic Plates. 
I. The Incidence of Decay . 
The timbers used for these experiments were Oak and Pine in a fairly 
advanced stage of decay, since it was evident that, if no differences occurred 
between plates from sound and diseased timbers at that stage of decay, 
then it was unlikely that disease in an early stage could be detected. In all 
these cases the wood used was already air-dried, so as a preliminary each 
piece was exposed to moist air for three days. The specimens employed 
had a transverse surface not greater than 2| x 3J in. and were finally 
placed on Ilford process plates of that size. Controls of normal Oak and 
Pine were photographed by the same method at the same time. No 
differences could be found in the images obtained, except where the disease 
had progressed so far that the wood was almost powdery. Even then the 
image partook of the same character in both, e.g. in Scotch Pine the normal 
wood gave spring wood positive and autumn wood negative. The same 
occurred in the diseased wood except for a blurring effect where the decay 
was very advanced. It was soon evident from these results that this method 
would not be successful for detecting disease before it is macroscopically 
visible. 
II. The Effect of Varying Conditions of Temperature and Moisture 
and the recognition of Wood that has been kiln-dried. 
Samples of Scotch Pine and Oak were dried in air, over sulphuric 
acid, over calcium chloride, and by heating to ioo° C. for two days. Their 
weights were taken and negatives obtained in the dark. Then the samples 
were placed in moist air for three days, again weighed and images obtained 
in the dark. In the end each was dried at ioo° C. for several days till the 
dry weight was obtained, and from these results the percentage of moisture 
was calculated. 
Sample I. Scotch Phte. 
Condition. 
Weight 
in grm. 
Dry wt. 
Mois- 
ture 
%• 
Temp, of 
Exposiire. 
Time of 
Exposure. 
Spring 
Wood. 
. . Condition 
Autumn f 
Negative. 
la. 
Air dry 
32.897 
29.04 
13*3 
40° C. 
24 hrs. 
+ 

Fair 
b. 
Moist air 
36-275 
29.04 
24.9 
>) 
>> 
+ 
— 
No difference 
3 days 
from 1 a 
2 a. 
Dried over 
32.209 
29.45 
9*3 
7 ) 
» 
+ 
— 
Better than 
h 2 so 4 
1 a 
b. 
Moist air 
35 *o 85 
jj 
19-0 
77 
79 
+ 
— 
As in 2 a. 
3 days 
3 a. 
Dried over 
33*030 
2 9*765 
10.3 
9 7 
77 
+ 
— 
Good 
CaCl 2 
b. 
Moist air 
34.660 
77 
16-4 
77 
77 
+ 
— 
Not quite sa 
3 days 
intense as 
3 a 
4 a. 
Dried at 
5 3 *44 
77 
77 
+ 
— 
Good 
ioo° C. 
b. 
Moist air 
56.981 
8.6 
77 
7 7 
+ 

,, Better 
3 days 
definition 
than 4 a 
