POPULAR SCIENCE REVIEW. 
388 
Koenig likewise has been investigating the same subject ; tlie preservative 
action of sulphate of copper on wood has long been known, but several 
anomalies in its action required explanation. It is now found that the 
retention of copper in the pores of the wood is occasioned by the resinous 
matter present, those varieties which contain the most resin retaining the 
most metal ; whilst woody fibre from which the resin has been extracted by 
alcohol fixes no copper whatever in chemical combination. The utility 
of sulphate of copper as a preservative agent may depend in a great 
measure on the resinous copper salt which is formed, and by which the 
pores of the wood are more or less filled up, so that the attacks of insects 
are prevented. 
The valuable properties of charcoal as a means of absorbing and de- 
stroying the organic impurities in air by being filtered through it, have 
lately been applied on an extended scale to the ventilation of sewers, by 
Dr. Letheby and Mr. Haywood. The whole of the sewers in a space of 
fifty-nine acres in a crowded portion of the east of London have been 
for eighteen months past connected with the outer air by means of char- 
coal ventilators. The success of this plan has been perfect. Not only 
has all stench ceased from the ventilating gratings, but actual observa- 
tion has repeatedly proved that the odour of the sewer gases is not 
perceptible when they have traversed the charcoal, and a chemical 
examination of charcoal which has been in use during the whole of the 
period shows that the organic imasurata is completely changed by its 
wonderful oxidizing powers into alkaline nitrates. Thus, by the agency 
of a little wood charcoal, the gaseous emanations of sewage, which the 
experiments of Dr. Barker, and the clinical observations of Dr. Murchison, 
have shown to be the cause of a form of continued fever, aptly termed 
pathogenic, are completely arrested on their passage up the ventilating 
shafts, and changed into perfectly innocuous compounds. 
Now that paraffin oils are coming so largely into use, it may be of 
service to point out a very curious property which they possess. They 
seem endowed with a remarkable, facility for ascending capillary tubes. 
When placed in a lamp the oil (especially the lighter varieties) rises rapidly 
on the wick, and flows over the outside, and sometimes even it will creep 
up the sides of a bottle containing it, and penetrate between the neck and 
the stopper, escaping into the air. When confined in wooden casks it 
readily permeates the junctions of the staves if at all unsound, and covers 
the outside of the barrel. As it is commonly the custom to export paraffin 
oil in wooden barrels, this property should be well remembered, or serious 
accidents will occur. It has happened already that in the hold of a vessel, 
where several hundred barrels of oil were closely packed together, the more 
volatile liquid permeated the pores of the wood, and mingled with the air, 
forming a highly explosive mixture, which, on the approach of a light, 
instantly ignited and set fire to the vessel. 
The inalterability under atmospheric and most chemical agencies, which 
gave to paraffin its name, has been applied to considerable use in the 
laboratory of the chemist as a lubricant. Nothing is more common, and 
at the same time more annoying, than to find the stopper of some test- 
bottle obstinately refuse to move in spite of the different persuasive means 
