^236 
ACCOUNTS OF BORED WELLS EXECUTED IN FRANCE. 
The celebrated Steam-Gun is too well 
known, — and th^'unceasing interestit excites, 
far too generally admitted to require any 
particular notice. We shall, therefore, mere- 
ly observe, enpassanf, that a new barrel has 
lately been added, which increases the power 
and the precision of the instrument. 
The unique engine for showing the Com- 
bustion of Steel, is also well worthy the at- 
tention both of the curious or the general 
observer ; although the almost inconceivable 
velocity with which the wheel rotates, may, 
naturally, at the first moment, excite some 
alarm. 
Amongst the philosophical apparatus pos- 
sessed by the Society, may be mentioned a 
Lens or Burning-Glass of nearly four feet 
diameter. A Cal-oxi-hydrogen Microscope 
of great power and unrivalled splendour, con- 
structed by Cary, with various consecutive 
improvements made under the superintend- 
ence of the Society ; and a Laboratory — in- 
tended to facilitate the advance of science and 
practical knowledge. 
The Societyreceive for exhibition — Models 
of Inventions — Works of Art and Specimens 
of Novel Manufacture, subject to immediate 
delivery in the event of sale, or returnon de- 
mand; /ree /row aa^c/iarpe whatever to their 
depositors. It also affords every facility for 
the practical demonstration of discoveries in 
Natural Philosophy, or of any new applica- 
tion of known principles to Mechanical Con- 
trivances ; reserving only to the Council, 
the right of determining whether the pro- 
ductions offered are suitable to the Insti- 
tution. — 
SIMPLE AND EFFECTUAL MODE OF 
DEFECTING ERRORS IN LEVELLING 
OBSERVATIONS. 
In the best modern levelling-staves, as for 
instance, those for which a d elford medal was 
awarded to Mr. Gravatt, C. E., last year, 
by the Institution of Civil Engineers, the 
observation is at once read off by the survey- 
or, instead of being reported to him by the 
assistant ; a saving of time, and a diminu- 
tion of the sources of ei’ror, are the conse- 
quence. But still, if a surveyor, on the con- 
clusion of his field-work, suspects an error, 
he has no other means of discovering the 
place of the error, or removing the suspicion, 
but re-commencing the survey and repeating 
part, probably the whole, of his observations. 
A very valuable suggestion has been made 
by Mr. Heni’y E. Scott, which, if adopted 
by a surveyor, would, almost to a certainty, 
enable him, by merely referring to his field- 
book, and without the repetition of a single 
observation, to detect the place of the error, 
and correct it ; or, in case of there being 
none, to restore his confidence in his obser- 
vations and final result. Mr. Scott’s prac- 
tice is to have the front side of his levelling- 
staff graduated from the bottom as usual, 
and painted in black and white ; but in addi- 
tion, he graduates the rear-side of his 
staff, and paints it in red and white. 
This red graduation is in the sub-divisions 
the same as the front one, but the position 
and numbering of the principal divisions are 
different ; the first principal red division be- 
ing made at 0*75 ft. from the lower end of 
the staff, and numbered III. the next above, 
IV., and so on. Both sides of the staff are 
to be read off at each observation ; and it is 
evident, that two very different heights of 
each observed point will be recorded ; that 
from the red side being constantly 2’ 25 ft. 
higher than that from the black or the true 
one. A difference so wide, that the memory 
can never act disadvantageously in reading off 
the quantities on the two sides. An error in 
the levels can, by this mode of registering, 
be detected by a single glance ; for the sur- 
veyor has simply to ascertain the place 
where any two observations of the same 
point have not the regulated difference. If 
no case of this kind occurs, there arises a 
feeling of confidence in the accuracy of the 
whole level-survey, which can scarcely be 
shaken. 
ON BORED WELLS. 
This convenient, we may say elegant, me- 
thod of obtaining good water from great 
depths, without the labour of lifting it, is 
spreading extensively in France, principally 
owing to the enlightened and patriotic exer- 
tions of MM. Arago and Hericart de Thury. I 
The first, by his writings on the subject, and j 
his successive notices of the works as they are j 
executed, excites and keeps alive the atten- j 
tion of the whole French nation. 
For the same purpose, with regard to our 
own country, we shall, at all times, be gratified 
by receiving and publishing, correct and 
detailed accounts of Bored Wells, executed 
in England, &c. Cases of supposed failure 
in these attempts, where all the circumstances 
are known, would be as acceptable as those 
of success. Hints might be suggested for 
proceeding agairi with a prospect of arriving 
at the desired object ; or, if this is hopeless, 
the facts might be recorded and useless ex- 
penditure prevented in future similar cases. 
In preparing the accounts, attention should 
always be paid to the kind of strata passed 
through, their thickness, &c. The locality 
of the well should be accurately described, its 
contiguity to river, mountain, sea, lake, &c. 
or the contrary. The waters of infiltration, 
(land-springs, &c.,) should be noted; and 
the supply, qualities, temperature, and per- 
manent elevation of the water finally obtain- 
ed, should be very carefully observed and 
described. 
Among the more recent instances of suc- 
cess in well-boring in France is one not far 
from the bank of a river, in a meadow be- 
longing to the Chateau de Cange, about three 
miles from Tours. The water was found 
at 425 feet deep, and the supply is about 560 
imperial gallons per minute. At Elbeuf, two 
wells, contiguous to each other and to the 
river Seine, have been bored to nearly 500 
feet. They are remarkable for the volume, 
purity, and high temperature (61? Fahr.) of 
their wateis. In twenty-four hours after a 
storm, or violent rain, one of these wells 
becomes troubled, and its water issues turbid 
wdth clay or sand, precisely like that of the 
