Part I.] Pearson : Antiseptic treatment of Sleepers. 
21 
PART III. Discussion on results obtained by treating sleepers- 
A discussion on the results obtained in the experiments dealt with 
in the preceding chapter naturally falls under tw'o heads, e.g., (1) Method 
of treatment and (2) Results according to species of timber treated. 
1. Method OF Treatment. 
(i) General discussion. 
The sleepers, with few^ exceptions, were treated by four distinct 
processes, i.e., (a) Powellizing, (6) by the introduction of small quantities 
of high grade creosote, (c) with Chloride of Zinc followed by a coating 
of creosote oil and {d) by a full cell process using a mixture of Earth Oil 
and Creosote, introduced either by the Open Tank method or under 
Pressure. A few sleepers as recorded in section 7, part II, of this note, 
were treated with Creosote only. 
(m) Powellizing. 
The results obtained by Powellizing have so far been eminently satis- 
factory, but more so in the drier regions than in the very wet localities. 
The reason why this process should give good results is not easy to 
explain, as the ingredients used are arsenic and a saccharine solution, 
both of which are soluble in water and therefore liable to be leached out 
of the wood by excessive moisture. This fact seems to be established 
to a certain extent by the results obtained, but not sufficiently so to prove 
the fact, as even in very wet localities the treated Pine have lasted over 
9 years, whereas in an untreated state they do not last 2|- years when 
used as Railway sleepers. It is thought that by boiling the timber in 
a solution of arsenic and molasses and afterw-ards subjecting it to a 
drying process at high temperatures the fibre is sterilized and the solution 
taken up in combination with the inherent sap in the fibre, while the 
free sap is driven out by the heat. 
(m) Treatment with small quantities of high grade creosote. 
The idea of testing the durability of sleepers treated with small 
quantities of high grade creosote was done purely with the object of 
attempting to reduce the cost of treatment. The results obtained 
cannot be said to be altogether unsatisfactory considering the low coat 
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