all the mud in wet weather, and would lay the dust in dry.

6th. The noise of the passing carriages would be entirely deadened. There would be little vibration and jolting of carriages. They would run along such a wooden street with the same comfort to the riders as they would on the Mall in St. James's Park.

7th. The gas and water mains should be laid in a trough of cast iron, of sufficient size to hold them, extending along each side of the pavement, and might be covered with a cast iron top or lid, upon which the blocks or pavement would be laid; and when the gas or water pipes at any time required to be repaired, access could be had to them at one-fourth of the present trouble and expense.

8th. There would be at least thirty per cent. saved in the wear and tear of horses and carriages.

9th. In proportion as the wooden pavement was introduced, the roads in the vicinity of London would be improved, by the same granite stones, when broken, being applicable to the making or mending of those roads, in preference to the use of the flints.

10th. In the same proportion as the street would be cleared of filth, mud, and vegetable matter undergoing decomposition, (by which the air is so much contaminated,) so would the health and longevity of your citizens and inhabitants be preserved and extended. I am, Sir, Yours, &c.

JOHN FINLAYSON.

METHOD OF PRODUCING DAMP IN POWER-LOOM
FACTORIES.

GENTLEMEN,-From the many improvements which have been made, and essays written, on powerloom weaving, it would appear it has now become an object of extensive speculation; but it still labours under a very great disadvantage, (if the factories are built high,) viz. the want of a sufficient portion of damp. As I have never as yet heard or seen any hints with regard to remedying this, I beg to submit my plan for your examination, which, if found to deserve a place in your valuable Magazine, you will much oblige me by inserting.

It is well known that cotton-yarn has a very great affinity for moisture, so much so, indeed, as to increase very materially in weight by being hung over vessels filled with water. It is likewise known that the atmosphere becomes so loaded with humidity from the presence of water, as to affect the hygrometer

very considerably. On these properties this method of moderating the drought in power-loom factories depends. It is to place vessels filled with water under the looms, of a sufficient length and width, and about one inch deep, so formed that the damping surface may be increased or diminished at pleasure, by supplying or taking away the water. The atmosphere may thus be always kept at a degree of humidity, according as the work requires it, by referring to a hygrometer, placed there for the purpose; and, consequently, the yarn will be prevented from becoming brittle and breaking, as it invariably does when there is too great a portion of drought. Should the moisture seem to come too direct on the yarn, let the vessels be placed in any other part of the house, probably over the looms, so that the atmosphere be first affected.

The vessels in each flat ought to be all on one level, and connected together, so that they may be filled or emptied at once, and in any proportion, from a pipe on the outside, by the overseer, independent of the workers within. The water for this purpose being pumped up by the engine, may be changed every two or three days, so as to prevent any smell arising from stagnation.

Fig. 3 represents a section of this plan, wherein A A are the vessels

to be placed under the looms, and connected by means of the pipes B, B, to another, D, D, in the passage, which is supplied from the cistern C, and furnished with proper stop-cocks, &c. and a graduated glass tube for the purpose of raising or lowering the water in the vessels when required.

I am, yours, &c.

South Hanover-Street, 6th May, 1825.

J. A.

ON DRAINING OLD WASTES IN COAL MINES. GENTLEMEN,-I beg leave to hand you the following, as an answer to a query proposed by a "Coal Hewer" in No. LXVIII. of the present volume of your Magazine. The plan that I propose, I have seen acted upon with great effect in a case, as far as I can judge, nearly similar to that mentioned by your Correspondent. The pit, A, (fig. 4,) in which the workings were to the dip, got so deluged with water, that the men were obliged to abandon it: another pit, B, was sunk at some distance from the old one, the workings of which were to the rise, so that the men were always in danger of breaking in upon the old workings of the pit

A.

The plan pursued to obviate the danger was this: they kept three bores always before them, of about one, or one and a half inch diameter each; one in the centre as at C, of 30 feet long, the other two, E and D, went off at angles of 45 degrees, they were 24 feet long. The use of the latter being in case any of the old workings might extend farther at the sides than the centre C, as shown at G and F, so that they were always sure to give timely warning of the approach to the old waste. These bores or tunnels can be so enlarged

or diminished as to discharge only
as much water as the engine is ca-
pable of delivering. But there is
a plan I have seen followed in pits
where the workings were both to
the rise and dip, and when the wa-
ter was coming in such quantities
as to deluge the low workings, as
in the above case; a dam was made
of timber across the mine as at H,
the seams of which were caulked
with oakum, the ends of the logs
were sunk in the sides of the mine
from three to four feet horizontally,
the lower one being sunk in the
pavement, a pipe was put through,
having a flaunch on one end to fix
it inside, and a stop-cock at the
other to regulate the quantity of
water as shown at L; at the top
of the dam was an air-tube, K, to
take away any risk of the dam
bursting. The sluice door at I is
for the convenience of the workmen
caulking the seams inside of the
dam; it opens off the inside, and
the pressure of the water keeps it
tight. This plan is of great service
in insuring the safety and ease of
the men while working, and as it
will in some degree answer the pur-
pose of your Correspondent, I shall
feel obliged at your inserting it.
I am, yours, &c.

Glasgow, 28th April, 1825.

S. S.

ON WATER TRAPS FOR COMMON SEWERS. GENTLEMEN,-It has often occurred to me when passing through the streets in London, on seeing men going down into the common sewers to cleanse them, that some improvement might be made to save the men the very disagreeable, and, I may say, dangerous mode at present pursued. Being a subscriber to your valuable little work, I have again had my thoughts roused to this subject, by seeing some of your Correspondents' ideas made public, for "Water traps to prevent smell from common sewers.' Now I think my idea to remedy what I have above complained of and my idea to simplify your water trap-may, with the greatest ease, be brought together: the accompanying sketch may serve to explain my thoughts:

a, (fig. 5,) is the common sewer; b, a pit (made to what depth, and what shape you think best,) along side the sewer; c, the grating from the street; d, a trunk to communi

cate with the sewer and the pit,
but elevated at the entrance into
the sewer, that the other end may
dip into the water to serve as a
water or stink trap; e, the water; f,
the dirt and other rubbish that will
not float away. Now, the intention
of the pit is, to save the men
going down into the sewer, as the
grating may be thrown back every
three, six, nine, or twelve months,
to take out the dirt from the bottom,
and the trunk is my idea to serve
as a trap (to prevent all unpleasant
smell) on a simple plan. Should
the above be thought worthy of a
place in your Magazine, that by its
simplicity it may be found worth
a trial, and by that trial it may be
found to answer the purposes it is
intended to remedy, I shall feel
happy in having added a comfort to
the good city of Glasgow.
I am, yours, &c.

London, 8th April, 1825.

W. O.

ANSWER TO THE QUERY AS TO THE ALTITUDE OF A TERRESTRIAL OBJECT.

GENTLEMEN,-I observe in your instructive and useful Magazine a query from X. Q viz. "The altitude of a terrestrial object situated above the horizontal plane, being 30° 45', 37° 43', and 60° 12′; it is required to determine from thence

the perpendicular height, with or without a demonstration."

I fear that your Correspondent has left out one link in the data that cannot be dispensed with, namely, the length of a side of one of the triangles which his

other data supplies, since the angular altitudes of the object A b, fig. 6, as seen from c, d, e; and of Ă B, as seen from C, D, E, will be the same respectively.

Your Correspondent is probably aware that if C, D, B, be in the same straight line and parallel to the horizontal level, the question is answered by the application of a problem in plane trigonometry, provided the distance between C and D is measured; and in that case the measure of the altitude from E becomes unnecessary. For, in the triangle A, B, D, since the angle at B is a right angle, and since the angle at D is measured,

angle in the

the angle at A is known, but the
exterior angle A, D, C,
B, A, D, † A, B, D, :
triangle A, D, C, the angle at D is
known, and since the angle at C is
measured, the angle at A is
known, and the side D C is mea-
sured. Now, the sides A D and
A C may be found, since they and
the known side D C are as the
sines of their opposite angles re-
spectively. Let the side A D be
found; then as radius: AD :: Sine
angle A, D, B: side A B, namely,
the height of the object.
I am, yours, &c.

A SAILOR.

ON DRAINING OLD WASTES IN COAL MINES. GENTLEMEN,-G. M.'s answer to the query by a "Coal Hewer," in No. LXX. of the present volume of your Magazine, is imperfect. If the boundary of the waste is ascertained exactly, there will be no difficulty or danger in driving the new workings within four yards of the waste, and after this is done, a bore of an inch and half in diameter should be put through upon it, near the bottom of the coal, so that it may carry off the most of the water. If, again, more water issues from this bore than the engine can discharge, a plug should be put in it, having a cock, so that the quantity of water may be regulated thereby; but if, on the other hand, the engine can discharge more, a second bore may be put through, as it would be difficult to enlarge the first, on account of the run of water. G. M. proposes to make

the bore or mine communicate with the waste above the surface of the water, which would be very difficult, and, in most instances, (with a bore,) impossible; because, if the waste is filled with water from the pavement to the roof, as it most likely will be, no communication could be made from the same seam of coal with a bore, to communicate with the waste above the surface of the water contained in it, as it is intended to communicate with the waste to the dip of the old field. That this is evident will appear to him.

If there is no plan extant of the old waste, and it cannot be exactly ascertained, a bore should be kept going at least four yards a-head of the workman who is driving for it. I am, yours, &c.

Kilwinning Colliery, 4th May, 1825.

A. K. J.

ON THE CRANK.

GENTLEMEN,-In No. LXIX. of the present volume, I observe a letter by A. B. on the crank, and

one on the water-wheel. In the former of these, A. B. begins by complimenting W. C. on lending

ON MICROSCOPES.