month in camp, or in any town, he ufually goes to the chace twice a week. He hunts the ftag, the roebuck, the antelope, and fometimes the tyger. When notice arrives that this laft animal has been obferved to quit the forefts, and ap. pear in the plain, he mounts his horfe, followed by all his Aby ffinians, his fpear-men on foot, and almost all the nobility armed with fpears and bucklers. The traces of the beaft being found, the hunters furround his hiding place, and con

tract the circle by degrees. As foon as the creature, who is ufually hid in fome rice ground, perceives his enemies, he roars, and looks every where to find a place of elcape; and when he prepares to fpring on fome one to force a paffage, he is attacked by Ayder him. felf, to whom the honour of giving the firft ftroke is yielded, and in which he feldom fails. Thus the pleasures of the fovereign are varied to infinity.

NATURAL

On a new Method of preparing a Teft Liquor to fhew the Prefence of Acids and Alkalies in Chemical Mixtures. By Mr. James Watt, Engineer; communicated by Sir Jofeph Banks, Bart. P. R. S. From Vel. lxxiv. of the Philofophical Tranfactions.

merly the teft of the point of faturation of mixtures of acids and alkalies, which was principally ufed; but fince the late improvements in chemistry it has been found not to be fufficiently accurate, and the in. fufion of tournefol, or of an arti. ficial preparation called litmus, have been fubftituted in the place of it.

The infufion of litmus is blue, and becomes red with acids. It is fenfible to the prefence of one grain of common oil of vitriol, though it be mixed with 100,000 grains of water; but as this infu fion does not change its colour on being mixed with alkaline liquors, in order to discover whether a liquor be neutral or alkaline, it is necef. fary to add some vinegar to the lit mus, fo as juft to turn the infufion red, which will then be reftored to ics blue colour, by being mixed with any alkaline liquor. The blue infufion of litnus is alfo a teft of the prefence of fixed air in water, with which it turns red, as it does with other acids.

The great degree of fenfibility of this teft would leave very little reafon to fearch for any other, were there reafon to believe that it is always a teft of the exact point of faturation of acids and alkalies, which the following fact feems to call in queftion.

I have obferved, that a mixture of phlogisticated nitrous acid with an alkali will appear to be acid, by the teft of litmus, when other tefts, fuch as the infufion of the petals of the fcarlet rofe, of the blue iris, of violets, and of other flowers, will fhew the fame liquor to be alkaline, by turning green fo very evidently as to leave no doubt.

At the time I made this difcovery, the fcarlet rofes and feveral other flowers, whofe petals change their colour by acids and alkalies, were in flower. Iftained paper with their juices, and found that it was not affected by the phlogisticated nitrous acid, except in so far as it acted the part of a neutralizing acid; but I found alfo, that paper, ftained in this manner, was by no means fo eafily affected by acids of any kind as litmus was, and that in a short time it loft much of that degree of fenfibility it poffeffed. Having oc cafion in winter to repeat fome experiments, in which the phlogisti cated nitrous acid was concerned, I found my ftained paper almost uselefs. I was, therefore, obliged to

fearch

fearch for fome fubfitute among the few vegetables which then exifted in a growing ftate; of thefe I found the red cabbage (brassica rubra) 10 furnish the best teft, and in its fresh ftate to have more fenfibility both to acids and alkalies than litimus, and to afford a more decifive teft, from its being naturally blue, turning green with alkalies, and red with acids; to which is joined the advantage of its not being affected by phlogisticated nitrous acid any far ther than it acts as a real acid.

To extract the colouring matter, take thofe leaves of the cabbage, which are fresheft, and have most colour; cut out the larger ftems, and mince the thin parts of the leaves very fmall; then digeft them in water, about the heat of 120 degrees, for a few hours, and they will yield a blue liquor, which, if ufed im. mediately as a teft, will be found to poffefs great fenfibility. But as this liquor is very fubject to turn acid and putrid, and to lofe its fen. fibility, when it is wanted to be preserved for future ufe, the following proceffes fucceed the best.

1. After having minced the leaves, fpread them on paper, and dry them in a gentle heat; when perfectly dry, put them up in glafs bottles well corked; and when you want to use them, acidulate fome water with vitriolic acid, and digeft, or infufe, the dry leaves in it until they give out their colour; then frein the liquor through a cloth, and add to it a quantity of fine whiting or chalk, ftirring it frequently until it becomes of a true blue colour, neither in

clining to green or purple; as foon as you perceive that it has acquired this colour, filter it immediately, otherwife it will become greenish by longer standing on the whiting.

This liquor will depofite a smal quantity of gypfum, and by the addition of a little fpirit of wine will keep good for fome days, after which it will become a little putrid and reddifh. If too much fpirit is added, it deftroys the colour. If the liquor is wanted to be kept longer, it may be neutralized by means of a fixed alkali instead of chalk.

2. But as none of thefe means will preferve the liquor long without requiring to be neutralized afresh, juft before it is ufed; and as the putrid and acid fermentation which it undergoes, and perhaps the alkalies or fpirit of wine mixed with it, feem to leffen its fenfibility; in order to preferve its virtues while it is kept in a liquid state, some fresh leaves of the cabbage, minced as has been directed, may be infused in a mixture of vitriolic acid and water, of about the degree of acidity of vinegar; and it may be neutralized, as it is wanted, either by means of chalk, or of the fixed or volatile alkali. But it is neceffary to obferve, that if the liquor has an excefs of alkali, it will foon lofe its colour, and become yellow, from which state it cannot be reftored; therefore care fhould be taken to bring it very exactly to a blue, and, not to let it verge toward a green*.

3. By the fame process I have

made

made a red infufion of violets, which, on being neutralized, forms at prefent a very fenfible teft; but how long it will preferve its properties I have not yet determined. Probably the coloured intufions of other flowers may be preferved in the fame manner, by the antifceptic power of the vitriolic acid, fo as to lofe little of their original fenfibility. Paper, fresh ftained with thefe telts in their neutral ftate, has fufficient fenfibility for many experiments; but the allum and glue which enter into the preparation of writing-paper feem in fome degree to fix the colour; and paper which is not fixed becomes fomewhat tranfparent, when wetted, which renders fmall changes of colour imperceptible; fo that where accuracy is required, the teft fhould be used in a liquid ftate t.

fore; and her difcharges at that time were fo great as to bring her into a very weak condition. She foon perceived fome uneafinefs, attended with a fwelling, on one fide, which, after a few months, become too large to diftinguish whether it was greater on one fide or the other. As the fwelling was found to arife from water, it was drawn off, which was in the year 1757. She was never afterwards pregnant; but the catamenia continued regularly till the ufual period of their ceffation. When I firft faw her, which was in the year 1780, fhe had been many times tapped, and fhe was then full of water. Her appearance was truly deplorable, not to fay fhocking. She was rather a low woman, and her body fo large as almost wholly to obfcure her face, as well as every other part of her with all fhe was tolerably chearful, and feldom regarded the operation. I faw her just before we took away 106 pints of water, and I begged leave

to take a measure of her. She was

fixty-feven inches and a half in circumference, and from the cartilago enfiformis to the os pubis thirty-four inches. Her legs were now greatly fwelled; but this, and every other fymptom of which the complained, evidently arofe from the quantity and weight of water. She neither ate nor drank much, and made but a fmall quantity of urine.

The operation of drawing off the water was generally performed on a Sunday, as the moft convenient day for her neighbours to affist her, and before the latter end of the week the was able to walk very well. She was first tapped in the year 1757, and died in August 1783.

Thus