Correspondence. _ 107 
M. de Quatrefages has made some experiments, which solves the prob- 
ase ich are 
5 . . 
formed into hyponitric acid, under the influence of a little oxygen. 
the termites, and have so penetrated into the deeper termitic cellules, 
that none have escaped. 
As the application of gas in many cases must be inconvenient, it is 
recommended to prepare the wood before employing it in construction. 
erhe method hitherto employed for preserving woods, have had refer- 
ence rather to protection against decay than insects. There is an ex- 
ception in the proces of Bethell, which consists in saturating the wood 
with a bituminous oil rich in naphthaline, a material proceeding from 
the distillation of the bitumen of coal. The cross-timbers of the Stock- 
ton and Barlington Railway, prepared in this way, ten years since, are 
still untouched ; and the same is true of the timbers of part of the Lon- 
e 
Sensibility that enables it to mark the direction, velocity, continuance, 
and succession of changes in the winds; and moreover, the apparatus 
i io h as are 150 
