CARBOLIC OR PHENIC ACID AND ITS PROPERTIES. 479 
themselves according to their respective densities: it certainly seemed, however, more 
probable that they would obey the ordinary law of diffusion. 
Mr. Forbes, in reply, begged to remind Professor M‘Donald that he did not belong to 
any particular school of geology, and with regard to the quartz cavities had always found 
them very irregular and by no means generally bounded by planes. Agreeing with 
Professor Morris that zeolites were usually formed as the result of aqueous infiltration, 
a circumstance which had occurred to himself showed that all were not in the same con¬ 
dition. Having had occasion to send a mass of volcanic lava containing zeolites to a 
lapidary to be cut and polished, it was found that the mass of the rock itself had been 
very considerably acted upon by the water which had been necessarily employed in the 
operation ; so much so, in fact, that it appeared incredible that the zeolites in the in¬ 
terior had been produced by the action of any aqueous solution. Dr. Muller he believed 
to be correct in regarding the minerals of Monte Somma as not consisting of true vol¬ 
canic products. But the case was different in other parts of the globe. For about 600 
miles along the Andes quartz in hexagonal crystals occurred in the volcanic rocks, and 
the microscopic examination of the quartz of recent lavas by Mr. Sorby showed abun¬ 
dance of glass cavities which could only result from fusion. Mr. Forbes believed that 
under the influence of heat, water, and great pressure, results might obtain which could 
not under other circumstances, as with heat alone, be brought about; and that many 
of these changes would occur even below a red heat. In reply to Dr. Williamson’s 
question, he had intended to convey the idea only of the temporary stratification of the 
primeval atmosphere. The element time must be taken into account in considering the 
effects of diffusion; and no doubt ultimately any such arrangement would be obliterated 
by intermixture. 
CARBOLIC OR PHENIC ACID AND ITS PROPERTIES. 
(.From a Lecture by Dr. Grace Calvert , delivered before the Society for the Encourage¬ 
ment of Natural Industry in France , and published in the\ Journal of the Society 
of Arts .) 
No doubt most persons present are aware that when coals are submitted to the action 
of a dull red-heat, in a retort, products are obtained which may be grouped into four 
classes. 
1 st. Gaseous products, commonly called coal gas, and which are now employed in so 
general a manner as means of illumination, sources of heat and motive power. 
2 nd. Water containing ammonia and ammoniacal salts, substances which chemistry 
purifies, modifies, and which are then utilized in agriculture, manufactures, and medicine. 
3rd. There distils with the above products a black, sticky substance, of an unpleasant 
odour, called tar. 
4th. There remains in the retort a solid, porous body, which is known to us all as 
coke. 
When the above-mentioned product called tar is submitted to distillation, water first 
comes over, then there distil jointly with this fluid, liquid carburetted hydrogens, which 
being lighter, float on it, and are therefore called light oils of tar; and, lastly, com¬ 
pounds heavier than water are collected, which bear the name of heavy oils. 
It is these heavy oils which were the first tar-products utilized in manufacture. Their 
consumption made such rapid progress in England, that special manufactories were es¬ 
tablished for their preparation, and these works were, for a long period, the' only ones 
in which tar products were produced. Most of them were established towards 1837, for 
the production chiefly of coal naphtha, used for many purposes, and heavy oils, employed 
for the preservation of railway sleepers, by a process discovered by Mr. John Bethell, by 
means of which they are preserved twelve, fifteen, or even twenty years ; whilst without 
it they decay after three or four years. I have much pleasure in calling your attention 
to a very remarkable and very complete work upon the creasoting of wood, by M. Fo- 
restier, chief engineer of the department of La Vendee, assisted by M. Marin, an engi¬ 
neer. These gentlemen have made, as you can see, numerous experiments, the result of 
which is, that wood thus treated is preserved from decay in water as well as under 
ground, and, what is very important, it is no longer destroyed by that very destructive 
insect the teredo. 
