render the water heavier, and more nauseous to the taste; it is therefore adviseable to always strain sea water before it is drunk.

The luminous property does not appear to have any connec

tion with the œconomy of the animals that possess it, excepting in the flying insects, which by that means discover each other at night, for the purpose of sexual congress.

USEFUL

Improvements in the Aquatinta Process, by which Pen, Pencil, and Chalk Drawings can be imitated. By Mr. J. Hassell.

[From the Transactions of the Soci ty for the Encouragement of Arts, &c. Vol. XXVIII. for 18.0]

SIR,

ERCEIVING the various methods of imitating drawings and sketches in the graphic art, fall short of an accurate imitation of the black-lead pencil, I determined on an attempt some years since, which, after repeated experiments, I flatter myself, I have fully established.

The manner is totally new, and solely my own invention. By the method I adopt any artist can sketch, with a black lead pencil, his subject immediately on the copper; and so simple and easy is its style, that an artist can do it with five minutes study.

By this manner, the trouble in tracing on oil paper, and other retracing on the etching ground is avoided, and the doubtful handling of an etching-needle is done away, as the pencilling on the copper is visible in the smallest

touch. It has also another perfection, that by using a broader instrument it will represent black chalk, a specimen of which I procured Mr. Mann, the landscapepainter, to make a trial of. I have herewith sent the said specimen, marked C, and Mr. Munn's name is affixed to the same. This subject he actually drew upon copper, under my inspection, in less than twenty minutes, the time he would have taken, perhaps, to do the same on paper; in fact, it can be as rapidly executed on copper as on paper.

It is particularly pleasant for colouring up, to imitate drawings, as the lines are soft, and blend in with the colour. It is a circumstance always objectionable in the common method of etching, that those so tinted can never be suffi ciently drowned, nor destroyed, and always present a wiry hard effect.

It is equally adapted to historical sketching, and might be the means of inducing many of our eminent painters to hand down to posterity their sketches, which, at present, they decline from the irksome trouble attending the repeti

tion of retracing their performances, and the doubtful handling of the etching-needle, which can never give a sufficient breadth and scope to their abilities.

I have, sir, forwarded, in an annexed paper, the different specimens, for the inspection of the gentlemen forming the Society of Arts, &c. &c.

In making my specimens I have thought it necessary to show, if by any accident a part might fail, that it could be retouched a second time, and oftener if wanted; in this particular its simplicity stamps its use.

To elucidate the foregoing proposition, I purposely caused a part of the distance to fail in specimen AA; this is repaired, you will perceive, in specimen B, and the sharp touches wanted to perfect the sketch are added.

I beg also to state, it is not the style usually termed soft ground etching that process is always uncertain, cannot be repaired, and will only print about two hundred impressions; whereas the specimens herewith sent will print upwards of five hundred with care.

Should the Society for the Encouragement of Arts, &c. drem the subject worthy of their reward, I shall feel proud in communicating its process, and flatter myself the arts and artists will feel a peculiar addition and pleasure in its utility. Permit me, sir, to subscribe myself, with all respect,

Your obedient humble servant, JOHN HASSELL, Landscape-Draftsman, 11, Clement's Inn, Strand. March 20, 1810. To C. Taylor, M.D. &c. &c.

Process of Drawing upon Copper, to imitate Black-lead Pencil, or Chalk.

A remarkable good polish must be put on the copper with an oilrubber and crocus-martis well ground in oil; after which it must be cleaned off with whiting, and then rubbed with another clean rag.

You are then to pour over your plate the solution to cause ground, which is made as follows:

No. 1.-1hree ounces of Bur gundy pitch.

One ditto of frankincense. These are to be disso.ved in a quart of the best rectified spirits of wine, of the strength to fire gunpowder when the spirits are lighted.

During the course of twentyfour hours this composition must be repeatedly shook, until the whole appears dissolved; then filter it through blotting-paper, and it will be fit to use.

In pouring on this ground, an inclination must be given to the plate, that the superfluous part of the composition may run off at the opposite side; then place a piece of blotting-paper along this extremity, that it may suck up the ground that will drain from the plate, and in the course of a quarter of an hour the spirit will evaporate, and leave a perfect ground that will cover the surface of the copper, hard and dry enough to proceed with.

With an exceeding soft blacklead pencil sketch your design on this ground, and when finished. take a pen and draw with the following composition, resembling ink if you wish your outline to be thin and delicate, cause the

pen

pen you draw with to be made with a sharp point; if you intend to represent chalk drawing, a very soft nib and broad-made pen will be necessary, or a small reed. No. 2. Composition, resembling ink, to draw the design on the copper.

Take about one ounce of treacle or sugar-candy, add to this three burnt corks reduced by the fire to almost an impalpable powder, then add a small quantity of lampblack to colour it; to these put some weak gum-water (made of gum-arabic), and grind the whole together on a stone with a muller: keep reducing this ink with gumwater until it flows with ease from the pen or reed.

To make the ink discharge freely from the pen, it must be scraped rather thin towards the end of the nib, on the back part of the quill; and if the liquid is thick, reduce it with hot water.

Having made the drawing on the copper with this composition, you will dry it at the fire until it becomes hard; then varnish the plate all over with turpentinevarnish (No. 3,) of the consistency of the liquid varnish sent with this as a sample.

It will now be necessary to let the varnish, that is passed over the plate, dry, which will take three or four hours at least; but this will depend on the state of the weather; for if it should be intensely hot, it ought to be left all night to harden.

Now the varnish is presumed to be sufficiently hard, you may rub off the touches made with the foregoing described ink with spittle, and use your finger to rub

them up; should it not come off very freely, put your walling-wax round the margin of your plate, and then pour on the touches some warm water bot care must be taken it is not too hot.

The touches now being clean taken off, wash the plate well and clean from all impurities and sediment of the ink, with cold soft water, then dry the plate at a distance from the fire, or else in the sun; and when dry, pour on your aquafortis, which hould be in cold weather as follows:

To one pint of nitrous acid, or strong aquafortis, add two parts,. or twice its quantity of soft water.

In hot weather, to one part of nitrous acid add three parts of water.

In every part of this process avoid hard or pump water.

The last process of biting in with aquafortis must be closely attended to, brushing off all the bubbles that arise from the action of the aquafortis on the copper.

In summer time it will take about twenty minutes to get a sufficient colour; in winter perhaps half an hour, or more. All this must depend on the state of the atmosphere and temperature of your room. If any parts require to be stopt out, do the same with turpentine-varnish and lamp-black, and with a camelhair brush pass over those parts you consider of sufficient depth; distances and objects receding from the sight of course ought not to be so deep as your fore-grounds; accordingly you will obliterate them with the foregoing varnish, and then let it dry, when you will apply the aquafortis a second time,

and

and repeat this just as often as you wish to procure different degrees of colour.

Every time vou take off the aquafortis the plate must be washed twice with soft water, and then set to dry as before.

To ascertain the depth of your work, you should rub a small part with a piece of rag dipped in turpentive, and then apply the finger, or a piece of rag rubbed on the oil rubber, to the place so cleared, and it will give you some idea of the depth.

The walling-wax is taken off by applying a piece of fighted paper to the back of the plate all round the opposite parts of the nargin where the wax is placed then let the plate cool, and the whole of the grounds, &c. will easily come off by washing the plate with oil of turpentine, which must be used by passing a rag backwards and forwards, until the whole dissolves: it is then to be cleaned off by rags; and care must be taken that no part of the turpentine is left hanging about the plate. The plate should only pass once through the press.

Directions respect:ng Grounds. No. 1.-The ground in hot weather must have an additional one-third of spirits of wine added to it for coarse grounds to represent chalk, and one-half added to it for fine grounds, to represent black-lead pencil; and always to be kept in a cold place in summer, and a moderate warm situation in winter.

N. B.-If any parts are not bit

strong enough, the same process is to be repeated.

Gum-water must be made in the proportion of half an ounce of gum-arabic to a quarter of a pint of water.

Turpentine-varnish is composed of an ounce of black rosin to an eighth part of a pint of spirits of turpentine: if the weather is excessively warm, it ought to be made with the sixth part of a pint of spirits of turpentine.

Tracing rag should be made of a piece of Irish linen, not too much worn, the surface of which is to be rubbed with another rag dipped in sweet oil, just sufficient to retain a small portion of vermilion or pounded red chalk." This must be placed with the coloured part towards the ground of the plate, and the drawing or tracing laid upon it, which must be traced very lightly with a blunt point or needle.

Method of preparing Ox-gall in a concentrated state, for Painters, and for other uses. By Mr. Cathery.*

[From the Transactions of the Society of Arts, &c. Vol. LVIII for 1810.]

It has long been a desideratum to find out a method of preparing ox-gall for the use of painters, so as to avoid the disagreeable smell which it contracts by keeping in a liquid state, and at the same time to preserve its useful properties. I have invented a method of doing

it