Copy of a Letter from BENJAMIN SILLIMAN, Professor of Chemistry at Yale College, to DAVID MELVILLE, Patentee of the Improved Gas Apparatus.

Mr. David Melville,

SIR,

New Haven, August 18th, 1814

Your favour of the 8th instant is before me, and I beg you to accept my thanks for the enclosed engraving of your apparatus for the gas lights. The print is very handsome, and does good justice to your apparatus. When you were so obliging as to show it to me, during my visit at Newport, last summer, I was agreeably surprised to see an apparatus so perfect, contrived and constructed in this country, where the subject of the gas lights is less generally understood than in Europe. I think your apparatus simple and effectual, and well adapted to the purposes of manufacturing establishments, and the flames which you shewed me were brilliant, and burned without smoke or smell.

Nothing, but a general knowledge of the gas lights, is ne cessary to introduce them into the large manufacturing esta blishments, which are now becoming so numerous in our country. They have the strongest recommendation which can address itself to practical men; viz. economy. Those who feel particularly interested to know the details of the subject, may find all the information which they can reasonably desire, in very elaborate and minute reports, drawn up from actual experiments, made on a very great scale, in one of the largest manufactories in England, by Mr. Murdock; and in various papers, by Mr. Cook, and others, for which reference may be had to Nicholson's Journal, and other periodical works on science and the arts. It will be found, by referring to these, and other similar sources of information, that the saving pro

duced by the gas lights as a substitute for oil and tallow, is very great, and in large establishments amounts to a heavy sum. It is probable that circumstances in this country might produce some variation in the result, the degree of which experiment alone can determine. The gas lights are probably less adapted to private families than to public establishments, because, the care and skill which are requisite, are more than can be reasonably expected among common domestics. But, in large manufactories, the business of preparing the gas and of attending on the lights, will of course be assigned to a particular person, who, with a common share of ingenuity, will soon acquire the habit of doing this, as he would any other thing.

Economy is not all which recommends the gas lights; for, were they ever so cheap, if they did not, in a good degree, answer the desired purpose of affording a good light, no one would adopt them. The light from the combustion of the gas from fossil coal, when the coal is of a good quality, is remarkably brilliant and beautiful. I saw a large apothecary's shop in London, lighted with the gas from coal, and as the thing was then (1805) by no means so common in London, as at present, it drew a great concourse of people, every night, around the shop, and thus brought it into general notice. The proprietor of the shop was so civil as to shew me his apparatus, which was arranged in a cellar, beneath the room in which the lights were exhibited; and although the apparatus was a good one, I think it was inferior in several respects to yours. There was, however, one circumstance which struck me as particularly judicious, although I cannot say how generally it is adopted in other establishments of this kind; I allude to the placing of quick lime in the water of the apparatus intended to wash the gas; as the carbonic acid gas is the most troublesome foreign body which is commonly found mixed with the inflammable gas, the lime performs au important service, by removing it more rapidly than the water alone would do, or after it is saturated with it. I have tried many experiments on

different substances, for the purpose of obtaining inflammable gases, to afford light by their combustion. Some sorts of coal give only a poor gas, burning with a pale blue light, and with only a feeble illumination; while from other kinds of coal, the gas gives a rich brilliant light, hardly surpassed by any thing. I believe the Cannel coal is generally used in Great Britain: I have found some specimens of the Richmond coal (Virginia) answer very well; but, few substances which I have tried, afford a richer gas than walnut meats (as they are commonly called), and even the whole of the walnut (shell and all) answers very well, and a quart of walnuts will afford a barrel of gas. Walnuts are too dear in the maritime parts of New Eng land to be substituted for coal, but the hint might be of advantage in some parts of this country, where walnuts abound, and coal is dear. The light from the inflammable gases, when of a good quality, is remarkably steady and uniform; as there is no wick, no snuffing is necessary; and workmen, in manufactories lighted in this manner, are not interrupted as they commonly are in trimming their lamps or snuffing their caudles; the light does not become dim occasionally, as that from lamps and candles does; nothing falls from the light, or can possibly fly from it to kindle cotton, linen, or other combustible substances, which abound in many manufactories; and, as the gas light is necessarily confined to the spot where it is used, and as any particular light can be instantly extinguished by simply turning the key of a stop-cock connected with that particular tube, or the whole can be put out by turning the key of the main tube, the security against fire becomes as complete as the nature of combustion will probably ever permit.

It is a circumstance also of no small importance, that a workman may regulate the quantity of light which he wishes, by properly adjusting the key of the stop-cock; if the workman wishes to go away for a time, and still does not choose to extinguish his light, he may, by cautiously closing the key of the stop-cock, reduce the flame to a mere point, which like a little

brilliant star, rests on the orifice of the tube, and will remain so for hours, with scarcely a perceptible consumption of gas; and when the key is again turned back, the light blazes out anew, with its former brilliancy.

Much more might be written on this subject, upon which, sir, you have requested my opinion, but perhaps it is not necessary. If apparatus, materials, and attendance, are not materially more expensive in this country than in England, the gas lights can, and without doubt will be advantageously introduced into our manufactories. I wish you success in your laudable efforts to make this useful and comparatively novel subject known to our countrymen, who are certainly inferior to the people of no country in ingenuity, resource, and enterprise, although they often are, in that perfect knowledge of the subjects to which they turn their attention; which, in older countries, results from a more minute division of labour and employment, and of course a more complete devotion to one object.

I remain, sir, respectfully,

Your most obedient servant,

BENJAMIN SILLIMAN.

References to the Plate representing Melville's Improved Gas Apparatus for lighting manufactories, &c. with gas lights, produced from pit or stone coal.

FIG. I.

AAA. The floor and part of the structure of the gasometer house.

B. A furnace in which the retort is set.

c. The door of the furnace where the fire is placed.

D. The ashes hole.

E. The damper, or register to regulate the draft of the furnace.

F. A cast iron retort (with the door fixed on) in which the coal is put to produce the gas.

G. The condenser and bath.

H. A pipe which conducts the gas from the retort to the condenser and bath, where it passes several times through water, by which it is washed and purified.

1. A cistern set in the ground and kept filled with water by means of an aqueduct, the water from which passes through the bath, to a drain from the gasometer house.

K. The gasometer, or reservoir, which is suspended in the cistern of water, by a rope or chain leading over sheaves to a balance.

L. A pipe which conducts the gas from the condenser, through the water in the cistern, to the gasometer, where it is reserved for use.

M. A stop-cock to let off the gas until it becomes inflammable, and to burn it from, when the gasometer is full, to prevent its escaping underneath.

N. A balance of weights, to hold the gasometer in suspension and (by taking one or more of the weights off) to give force to the gas when necessary.

Q. A pipe which conducts the gas from the gasometer house to the apartments where the lights are wanted; where it issues from the burners when vent is given to it, and on the application of a taper will burn with a brilliant flame without smell or smoke. The burners are fitted with keys by which the flames may be regulated, to give more or less light, or instantly extinguished, which operation may be performed on the whole at once, by means of a single key in the main tube.

FIG. II.

P. The form of the burner from which the gas issues, with the tube and glass, and key to regulate the flame, on a larger scale.

Specification of the mode of operation with Melville's Ime proved Gas Apparatus for lighting Manufactories, &c., with gas lights.

A quantity of coal in proportion to the number of lights re