Part IV.] It. S. Pearson: Antiseptic Treatment of Timber. ]09 
to be treated, tbe size and shape of the timber and the quantity to be 
dealt with. On these three factors will depend whether we adopt the 
Brush, Open Tank or Pressure processes. When a relatively small 
quantity of timber, say, for instance, a few hundred fencing posts, or 
constructional timber for a small bungalow has to be handled, applica¬ 
tion of two or more coatings of the antiseptic with a brush may suffice. 
In the event of a larger number of posts, telegraph poles, bridging or 
constructional material or from 30,000 to 50,000 sleepers having to be 
treated, the timber of which readily absorbs an antiseptic, an Open Tank 
plant may best answer the purpose ; while, for large quantities of sleepers, 
the timber of which does not readily absorb the antiseptic and where 
the plant is of a permanent nature, a pressure plant is advocated. 
The amount of the antiseptic to be introduced also requires con¬ 
sideration when deciding between Open Tank and Pressure plants ; 
thus, if 6 lbs. or more per cubic foot is the amount specified, unless the 
timber is especially absorbent, a Pressure plant will be required. 
(5) Choice of Antiseptics. 
With a view of determining the most suitable antiseptic for general use 
in India, the experiments detailed in Parts III, IV and V have been 
started. The choice of treatment may be said to lie between (i) 
Powellizing, (ii) Coal-Tar creosotes , patent or otherwise, (Hi) mixed 
Coal-tar creosotes and Petroleum products, ( iv ) Salts, such as Chloride of 
Zinc, Atlas, Fluoride solutions, Copper Sulphate, etc., and (v) mixed 
impregnation, first with a salt and then with a creosote oil. 
(i) Powellizing. 
In favour of Powellizing, we have experiments which have now been 
in progress for over six years, yielding satisfactory results. It is 
understood that, in Australia, Powellizing has been introduced in recent 
years, with the object of thoroughly testing its value for preserving 
Railway sleepers. Taking these facts into consideration, the writer is 
strongly in favour of following the lead given by the Australian Engineers 
and of giving this process an extensive trial in India. 
(ii) Coal-tar creosotes. 
Without doubt, Coal-tar creosotes are excellent preservative agents 
for timber, as they have withstood the test of time and still hold their 
-own against almost all other solutions. Such an assertion requires 
•qualification, in as much as all Coal-tar creosotes are not suitable for 
[ 239 ] 
