116 
MAGAZINE OF SCIENCE AND ART. 
commonly employed are of copper, insulated with 
gutta-percha, and encased in iron. Mr. Allan’s 
wire is one of iron, insulated with a now flexible 
material, sufficiently strong to afford a full protec¬ 
tion from all the contingencies to which such a con¬ 
ductor is ordinarily liable. The differences between 
the two are at first sight rather startling. Weigh¬ 
ing in some cases as little as one-tentli of the com¬ 
mon wire, wo obtain a conducting power three or 
even five-fold greater, while the relativo proportion 
of tho strength of the wire to its weight, is increased 
to a considerable degree. Add to those facts the 
diminished cost of construction, and the greater 
ease with which it can bo laid down.— Year Book of 
Facte, 1857. 
Preservation of Fresii Meats. —Mr. Geor.gc 
Hamilton, F.O.L., has read to the Liverpool 
Chemists’ Association a paper on tho “ Preservation 
of Fresh Meat.” After noticing tho different pro¬ 
cesses hithorto employed for the preservation of 
meat, ho detailod a long series of experiments which 
he had performed in 1852, and which had led him to 
tho discovery of the preservative properties of bin- 
oxide of nitrogen, which preserves meat from putre¬ 
faction without changing its colour or consistence; 
nor did it afterwards putrefy when exposed to tho 
air. Since the first announcement of theso experi¬ 
ments, at tho meeting of the British Association, 
held there in 1854, tho honour oi a similar discovery 
had been claimed for a French savan, but I’Anbfi 
Moigno, who was present in the chemical section 
when Mr. Hamilton's paper was read, says, in a 
letter to that gentleman, “ 1 shall be happy to make 
known your priority.’’ 'l'ho lecture was illustrated 
by a number of specimens of meat which had been 
prepared according to the process, ana which looked 
as fresh a 3 if thoy were just killed; and when 
cooked, as some of the specimens were, they could 
not bo distinguished from ordinary meat.—rear 
Book of Facts, 1857. 
Filtration of Water —Mr. H. M. Witt, F.C.S., 
Assistant Chemist to the Government School of 
Applied Sciences, has communicated to the Philo¬ 
sophical Magazine, No. 7(1, a paper "on a peculiar 
Power possessed by Porous Media (Sand and Char¬ 
coal) of removing Matter from Solution in Water.” 
The paper consists of certain experiments which 
were undertaken with the view of ascertaining by 
chemical analysis the more precise nature of the 
effects produced upon ordinary river-water, such as 
that of tho Thames, by its passage through filters 
composed of these media respectively, and of com¬ 
paring their powers; but it is Believed that tho re¬ 
sults obtained possess an interest extending con¬ 
siderably boyoud the question to assist in the 
solution of which they were made. The system of 
purification adopted by the Chelsea Water-works 
Company at their works at Chelsea, consisted 
hitherto (for the supply has by this time commenced 
from Kingston) in pumping the water up out of tho 
river into subsiding reservoirs, where it remained 
for six hours; it was then allowed to run on to the 
filter beds. These are large beds of sand and gravel, 
exposing a filtering surface of about three-fourths 
of an acre, or 32,G70 square feet; and the filtration 
taking place at the rate of one foot per hour, yields 
about 204,187 gallons of filtered water per hour. 
The filters are composed of the following strata in a 
descending order 
ft. in. 
No. 1. Fine sand . 2 6 
2. Coarser sand . 1 0 
3. Shells . 0 6 
4. Fine gravel. 0 3 
5. Coarse gravel. 3 3 
These several layers of filtering materials are not 
placed perfectly flat, but are disposed in waves, as 
seen in the sectional drawing ; and below tho convex 
curve of each undulation is placed a porons carthcu- 
waro pipe, which conducts the filtered water into 
tho mninB for distribution. Wo hare not tptco for 
the details, but quote .Mr. Witt’s brief summary of 
the most important results of this investigation 
It has been shown,—1st. That sand, charcoal, and 
probably other parous media, possess tho very pe¬ 
culiar property of removing, not merely suspended 
impurities, but even dissolved salts from solution in 
water; 2nd. That charcoal enjoys pre-eminently 
the power of abstracting organic matter from solu¬ 
tion; but that even sand likewise is capable of 
effecting the same result, though to a far less extent; 
3rd. That theso powers, possessed by both these 
media, increase in intensity to a certain extent with 
the degreo of imparity of the solution; 4th. That 
these properties of porous media have important 
bearings upon hygienic science, agricultural prin¬ 
ciples, and geological phenomena. Tho various 
analyses given show great variations ill the compo¬ 
sition of tlio river-water, between the two points at 
which experiments were made, vis., at Chelsea and 
Kiu" 5 ton, as well as at the different seasons of the 
year. Mr. Robert Hunt, F.K.S., Keeper of the 
Mining Records, lias addressed to Mr. Witt the fol¬ 
lowing examples, within his own knowledge, con¬ 
firmatory of Mr. Witt’s views. At l’orran-porth, 
some six or seven mileB north of Truro, the heaps 
of waste (deads) from the old mines contain con¬ 
siderable quantities of copper pyrites, which is, in 
tho process oi decomposition, converted into sul¬ 
phate of copper. This salt is washed out by tho 
rains, and tho solution flows through the sands 
(Mown sand) widely spread over that district. The 
sulphate of copper is separated by tho sand, and the 
sand containing the eopper is collected from time to 
time and sold to the copper-smelters. Again, at 
Botallnck Miso, the water which filters through tho 
rocks from the Atlantic Ocean in the levels which 
are worked ont under the bod of the soa is found 
to have lost much of its original saltncss.”— Year 
Book of Facts, 1857. 
NOTICE TO COKRESPONDENTS 
We are much obliged to Mr. C. G. Robertson, of Dem • 
troon, for tbe geological specimens he forwarded to us- 
We have placed them in the hands of a most competent 
authority, and hope to give a report upon them in our next 
number. The valuable paper on Ancient Indian History 
shall not be lost sight of. 
In answer to several enquiries as to the practical work" 
ing of tbe machine suggested by Mr. Dyer for the extrac¬ 
tion of the stumps of trees, he begs to say that arrange¬ 
ments are in progress for carrying out some experiments 
with a machine constructed on this principle. The result 
of these experiments shall be taithfully recorded. 
J. B., Bathurst_We should be glad to hear from you 
again on silk cultivation. 
r. T._Your highly interesting paper came too late 
for insertion in our present issue. It shall appear in our 
next. 
T. B_We are obliged for your hint. 
Received—Windsor Review. Month. Health Officer’s 
Report. Poem on the Wreck of the Dunbar. Victorian 
Agricultural and Horticultural Gazette. 
