After a good deal of inquiry, your committee
has been enabled to obtain information of the results of three of these
experiments.
The pine paving blocks upon Pennsylvania Avenue (experiment 23) were
first kiln-dried, and then immersed in a hot solution of sulphate of
iron.
The spruce blocks on E Street (experiment 24) were treated with chloride
of zinc, or, in other words, burnettized; but the mode of application is
not stated.
The pine blocks upon Sixteenth Street (experiment 25) were treated with
the residual products of petroleum distillation. It is stated that this
was the only process in which pressure was used.
In from three and a half to four and a half years the blocks were badly
decayed, and large portions of the streets were almost impassable, while
other streets paved in the same year with untreated woods remained in
fair condition.
It has been stated to your committee that this result, which did much
toward bringing all wood preserving processes into contempt, was chiefly
owing to the very dishonest way in which the preparation was done; that
in fact there was a combination between the officials and the
contractors by which the latter were chiefly interested "how not to do
it," and that the above results, therefore, prove very little on the
subject of wood preservation.
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