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1918.] The N.Z. Journal of Science and Technology. 
at my disposal by Professor Pickerill, Dean of the Dental Faculty, Otago 
University, and was fitted up according to the annexed diagram. 
For the purpose of examination, blocks that could be conveniently 
placed in the muffle were cut carefully to uniform size, 2 in. by 2 in. by J in., 
and the test applied as follows : The current was increased at a uniform 
rate, and the gases together with air were allowed to escape from the 
muffle through an asbestos chimney fitted with a mica window, and having 
a pilot gas-flame inside. At a temperature which differed for different 
Fig. 1.-—-Apparatus for determining the ignition temperatures of timber. 
woods the gases ignited, and burned continuously in the flue. This was 
taken as the ignition-point. A comparison of average figures may prove 
of interest: Rimu, 349° C.; kauri, 360° C. ; birch, 370° C.; totara, 320° C.; 
kahikatea, 290° C.; black-pine, 320° C. 
Impregnation .—Saturated solutions of the various salts were used, the 
method of impregnation being first to subject the wood to the action of 
a vacuum, while immersed in the solution, and then, when escape of air 
has ceased (by cessation of bubbling, which was found to be concluded 
after one hour), the atmospheric pressure was restored, thus forcing the 
