506 On the Quality of Creosote suitable for protecting 
tar which comes over on distillation between the temperature of 
about 350' F. and that of 760° F. It has a highly complex and 
variable composition. 
Amongst its constituents may be mentioned : phenol or car- 
bolic acid ; cresol or cresylic acid, closely allied in character 
to phenol ; naphthaline ; light tar-oils, passing over on distilla- 
tion at a temperature of about 600° F, ; heavy tar-products 
which remain behind in the retort at that temperature, viz., 
pyrene, chrysene, leucoline, cryptidine, pyridine, acridine, and 
other organic bases which occur in minute quantities in com- 
mercial creosote. 
The products of distillation of the liquid employed for 
creosoting wood are heavier than water, whilst the distillation 
products of animal and vegetable oils and fats, such as bone-oil, 
palm-oil, cotton-seed oil, resin-oil, and also shale-oil, have a 
lighter specific gravity than water. 
Carbolic and cresylic acid, distinguished for their powerful 
antiseptic properties, were until recently regarded as the most 
valuable constituents of creosoting liquids, and are still held by 
some of the highest chemical authorities as the chief consti- 
tuents upon which the efficacy of commercial creosote as a 
preserver of timber mainly depends. 
This generally received opinion has been called in question 
by Mr. Boulton, of the firm of Burt, Boulton, and Hayward, 
the well-known tar-distillers, who, in a paper read quite 
recently before the members of the Institution of Civil Engi- 
neers, on the strength of certain practical experiments, a long 
experience, and the testimony of several chemical experts, 
endeavoured to show that the efficacy of tar-acids as anti- 
septics has been overrated at the expense of the more stable 
and enduring properties of the tar-oils. At the same time 
Mr. Boulton admits that the percentage of tar-acids in the 
creosote to be used remains a contested matter of opinion. 
Notwithstanding all that has lately been said and written in 
favour of Mr. Boulton's view, it appears to me a hazardous pro- 
ceeding to rely on the efficacy of a creosoting liquid which 
contains as little as 3, 4, or even 5 per cent, of crude carbolic 
acid. 
In preserving old well-matured timber, such as is used for 
railway sleepers, and is less liable to perish than young immature 
wood, used for railings, hop-poles, and light wooden structures, 
creosote which is comparatively poor in crude carbolic and 
cresylic acid, but which is rich in heavy tar-oils, I can conceive 
may be quite efficacious in preserving such old timber ; but when 
we have to deal with young immature wood, full of sap, I do not 
think a creosoting liquid, containing as little crude carbolic 
