302 The N.Z. Journal of Science and Technology. [Sept. 
Saturated Steam. —Steam was admitted at the pressure required, the 
air being allowed to escape from the cylinder, which was brought to the 
maximum temperature as rapidly as possible. The theoretical tempera¬ 
ture corresponding to the pressure was obtained in all cases. 
Creosote. —The oil was maintained at the required temperature by 
means of a steam-coil, and was checked continuously by means of the 
try-cock. 
Readings were taken every ten minutes, and the weight of the piece 
was taken immediately before and after, as well as twenty-four hours after. 
Graphic representation of the results was adopted, since by this method 
a clearer analysis can be made. To gain the full advantage of this, 
suitable results were averaged, and a general curve obtained. The smooth 
curves are obtained from unseasoned wood; the dotted curves, from 
seasoned pieces ; other curves show the type of variation obtained amongst 
any set of trials. ^Where necessary exceptional curves will be explained 
seriatim. 
Discussion of Results. 
No change ofytemperature was recorded during the first ten to fifteen 
minutes, very approximately a quarter the time taken in Hunt’s experi¬ 
ments with 6 in. by 8 in. sleepers. So close is this relationship throughout 
these tests that it warrants the conclusion that any of the data obtained 
increased fourfold would apply with working accuracy to standard railway- 
sleepers. 
Once the temperature showed a rise it continued steadily falling off 
in rate towards the end, when the vacuum was drawn. This point, called 
by Hunt the “ end ” point, was considered to be attained when the rate 
of rise had fallen to less than 1-8° F. (1° C.) per ten minutes. This 
point was reached on the average after 1 hour 45 minutes. Continued 
heating in no case resulted in the interior temperature reaching that 
of the bath. The time taken to reach the boiling-point of water at 
the centre of the piece averaged 45-60 minutes (Hunt, 240 minutes). 
This point was not reached in any of the low-pressure steam or creosote 
trials. (See table.) 
Effect of Vacuum. —As might be anticipated, the application of a vacuum 
resulted in a rapid fall in the interior temperature from loss of heat due 
to evaporation. From the rapidity of this fall one might conclude that 
the vaporization takes place immediately throughout the piece, and not 
from without inwards. This may be the reason for marked splitting that 
occurs upon application of vacuum at high temperatures, since the pent- 
up vapour must force a passage to the exterior direct, and not slowly from 
cell to cell. The effect of this on the strength of the timber is to be con¬ 
sidered separately. 
Rate of rise of interior temperature was greatest with steam at 20 lb., 
and least with hot creosote. As shown by Hunt, green timber required 
more prolonged heating than seasoned, and the white variety of beech* 
took longer than the red wood. 
Changes in the Moisture-content, &c. —The results of these measurements 
were not so good as was anticipated. Both green and seasoned wood con¬ 
tinued to lose moisture during the first twenty-four hours following the 
* Forwarded me by District Railway Engineer as “ wliite-birch.” 
