616 
does not act as a poison in preserving the timber, because it could 
be seen that the Limnoria were embedded in wood still highly 
charged with creosote. 
o 
After carefully considering the subject, the author had no doubt 
that the process of creosoting preserved timber from the attack of 
marine insects only so long as the oil existed as a film or coating on 
the outside of the timber. Whenever the attrition caused by the 
motion of the sea removed this outer film or coating, and exposed 
the fibrous surface of the timber, the insect would then attack and 
perforate it, whether it were creosoted or not, its search being for a 
fibrous substance in which to burrow. The time that might elapse 
before the timber became assailable to these insects depended on 
the situation. Wherever there was little abrading action of the 
sea, the exterior film of creosote might be longer preserved; and 
where there was a considerable admixture of fresh water to check 
the growth, or at least the avidity of the insect, the effect of their 
ravages might be more gradual, or, in some situations, almost inap- 
preciable. But the result of the author’s observation and experi- 
ence led. him irresistibly to the conclusion, that on the northern 
shores of the country, where works are exposed to the open sea, creo- 
soted timber was readily perforated by the Limnoria, and could not 
be safely employed in any important part of a marine structure at 
or below half-tide level, a fact of great importance to the civil 
engineer. 
6. On some Thermic Properties of Water and Steam. By 
Professor W. J. Macquorn Rankine. 
The author refers to the general equation of the mechanical action 
of heat which Professor Clausius and he arrived at independently by 
different methods in 1849, and points out that the form of that 
equation, which was laid before the Society by him in a paper read 
on the 4th of February 1850, comprehends, as a particular case, the 
law which connects the volume of a given weight of steam with its 
temperature, pressure, and latent heat. He describes the use of 
that law, with proper numerical data, to' compute, in the absence of 
direct experiment, tables of the density and volume of saturated 
steam, more accurate than those founded on the assumption of the 
perfectly gaseous condition, as exemplified in tables which he pub- 
