THE DAVY LAMP FOUND PERFECT IN PRINCIPLE. 
215 
group, a series of rocks similar to the pre- 
ceding, and attaining to a very great thick- 
ness. 
These formations, however, appear to be 
newer than the Cumbrian rocks which have 
been investigated by Mr. Sedgwick, and 
which he also divides into three subordinate 
groups, all of which are included under the 
name of Cumbrian rocks. The first, or 
upper, is the Plinlimmon group : the second, 
or Snowden group ; and, thirdly, a lower 
group. The details on this last series of 
rocks were rather meagre, but we have no 
doubt that ample information will shortly 
be laid before the public. 
CHEMISTRY AND MINERALOGY. 
Monday y IQth August. 
Dr. Thomas Thomson, President. Dr. 
Dalton, and Dr. Barker, Vice-Presidents. 
Dr. Apjohn, and Mr. Johnston, Secreta- 
ries. Committee, — Mr. Davy, Mr. Vernon 
Harcourt, Dr. Daubeny, Mr. Graham, 
Mr. Connell, Dr. R. D. Thomson, Mr, 
Kane, Mr. Ferguson, Mr. Scanlan, 
Dr. Geo>ghegan, &c. 
The .Secretary presented to the Section 
printed copies of tables, exhibiting at a 
single view, the most important properties of 
simple and compound bodies, for defraying 
the expenses of the printing of which, £10 had 
been allocated at the last Meeting of the 
Association. 
1. A PAPER WAS THEN READ BY Mr. 
DAVY, UPON THE SUBJECT OF THE 
CORROSION OF IRON BY SEA WA- 
TER. 
The observations had particular reference 
to the injury sustained by the iron of buoys, 
subject to the infiuence of sea water in har- 
bours, as at Kingstown ; where it has been 
recently found, that the rings upon which the 
safety and utility of the buoys mainly depend, 
rapidly corrode and are destroyed. Mr. Davy 
turned his attention to the important object 
of providing a remedy, and preventing the 
corrosion of the iron ; and although his expe- 
riments had only recently been commenced, 
still he considered it proper, to bring the few 
results he had procured before the Section, 
for the purpose of exciting further inquiry. 
He found that zinc applied to iron prevented 
corrosion. Rings of this metal were cast into 
forelocks for the purpose of experiment, 
and were found to obviate the waste to which 
the iron had previously been subject. 
According to Sir Humphry Davy, the 
cause of the corrosion of copper, and metals 
in contact with sea water, is attributable to 
the access of atmospheric air. He consi- 
dered that if the air was preserved from 
coming in contact with the metal, no decom- 
position would ensue. Mr. Davy accord- 
ingly found, that copper exposed to the action 
of sea water free from the influence of air, 
was not liable, to corrosion, and that the 
effect was influenced by the depth of water. 
Specimens of metals were exhibited, which 
had been subjected to the influence of salt 
water free from air, and no corrosion had 
taken place ; other pieces of metal which were 
in contact with sea water subject to the 
influence of air, were observed to be much 
injured. Mr. Davy attributed the cause of 
the phenomenon to an electrical decomposi- 
tion. 
He stated further, that he had found zinc 
to preserve tin plate, both in fresh and salt 
water. 
Some observations were made by members 
of the Section, with regard to the action of 
sea water upon bar and cast iron. Some 
attributed the greatest corrosion to the for- 
mer, others to the latter. 
2. Mr. ETTRICK DESCRIBED AN IM- 
PROVEMENT WHICH HE HAD MADE 
UPON DAVY’S SAFETY LAMP, FOR 
THE PURPOSE OF OBVIATING AC- 
CIDENTS WHICH ARE ENTIRELY 
OWING TO THE CARELESSNESS OF 
WORKMEN. 
The Davy lamp, he stated, to be perfect in 
principle. The workmen are in the habit of 
enlarging the apertures in the wire gauze, 
and applying their tobacco pipes in order to 
obtain a light. The modifications recom- 
mended at present, were the introduction of 
very strong glass, to cover the gauze ex- 
ternally. The glass is again guarded by 
strong ribs of iron, so that the lamp may be 
exposed to considerable shocks without dan- 
ger of injury. A contrivance was also 
described by which the air was allowed to 
enter from below, by means of a gauze tube, 
but so managed, that the gauze could not be 
reached by the workmen. 
Various improvements upon the Davy lamp 
were noticed by different members. 
Mr. Graham stated, that he had been pay- 
ing considerable attention to the subject, and 
had found that when the gauze was steeped 
in an alkaline solution, the flame was pre- 
vented from passing so readily, and corrosion 
was obviated.* He considered the only 
adequate provision against accident to be 
the employment of a double gauze cover. 
3. Mr. KANE READ A COMMUNICA- 
TION IN REFERENCE TO PYROX- 
YLIC SPIRIT. 
The experiments which he had made upon 
this substance, corroborate the opinion of 
its composition entertained by Dumas and 
Pelligot, who term it methylene, viz. that it is 
a compound of an atom of carbydrogen, and 1 
atom water, having for its atomic weight 2. 
He had examined th^e action of sulphuric acid 
upon the liquid, and had obtained by dis- 
tillation, an acid capable of forming salts 
with bases. The composition of several of 
these, he had ascertained by determining 
the proportions of the acid, (or sulpho- 
* This is agreeable to the results obtained 
by Dr, Thomas Thomson many years ago. 
