Part IV.] R. S. Pearson: Antiseptic Treatment of Timber. 5 
though of value, especially to the investigator, should, owing to their 
limitations, be accepted with caution. 
2. Description cf the Laboratory Experiments. 
The experiments have been carried out on a fairly extensive scale, 
in so far as the number of antiseptic solutions tested is concerned, no 
less than 23 different salts and oils, or combination of both having been 
given a trial. The species of timber selected for trial were twelve in 
number, comprising all grades from extremely hard to some of the softest 
timbers of India. The tests carried out being of a strictly comparative 
nature, so as to keep all factors constant, the same species of timber 
were employed throughout, the specimens were cut to a uniform size 
of 18" x2"x2", and the period of immersion, when possible, was kept 
constant. It is an established fact that hard-woods absorb less solution 
than soft-woods during a stated period of immersion so that, to effectually 
protect a hard species, it is generally necessary to allow a longer period 
of immersion than would be necessary for a soft-wood species. Again, 
the amount of absorption permissible is directly proportionate to the 
Cost of the solution employed. These conditions were waived in order 
to obtain uniform results and to form a correct comparative estimate 
of the value of the various antiseptics employed. While carrying out 
the field experiments on a more extensive scale, as described in Part 
III, full consideration was given to the amount of antiseptic absorbed and 
to the corresponding cost of treatment of each individual species of 
timber. 
A further precaution taken v r as to experiment not only with tho¬ 
roughly seasoned timber, but also to prepare the necessary specimens of 
each species from the same log. In this way, possible variations in the 
structure and density of the two specimens of any individual species 
were avoided, and a true comparison of their relative merits, in a treated 
and untreated state, rendered possible. 
After treatment in the laboratory, a full description of which is given 
in the former note on the subject, the treated and untreated specimens 
w r ere put into the ground together, in a place known to be infested by 
white-ants, and each group inspected periodically. The only exception 
to the above procedure w r as in the case of the Powellized specimens, of 
which no less than 147 treated and untreated pieces were laid down and 
kept under observation. The only other point requiring mention is 
that, owing to the number of antiseptic solutions dealt with, all the tests 
could not be started at one and the same time, while each group had to 
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