of a uniform glare (as if almoft tranfparent) before the openings are shut, elfe the ugar or vapour is fure to fucceed to mifmanagement of this fort, and its effects are as follows.

If a perfon lays himself down to fleep in the room expofed to the influence of this vapour, he falls into fo found a fleep that it is difficult to awake him, but he feels (or is fenfible of) nothing. There is no fpafm excited in the trachea arteria or lungs to roufe him, nor does the breathing, by all accounts, feem to be particularly af fected; in fhort, there is no one fymptom of fuffocation but towards the end of the catastrophe, a fort of groan ing is heard by people in the next room, which brings them fometimes to the relief of the fufferer. If a perfor only fits down in the room, without intention to fleep, he is, after fome time, feized with a drowzinefs and inclination to vomit. However, this laft fymptom feldom affects a Ruffian, it is chiefly foreigners who are awaked to their dangers by a naufea; but the natives, in common with ftrangers, perceive a dull pain in their heads, and iEthey do not remove directly, which they are often too fleepy to do, are foon deprived of their fenfes and power of motion, infomuch, that if no perfon fortunately difcovers them within an hour after this worst stage, they are irrecoverably loft; for the Ruffians fay, that they

Ι

do

do not fucceed in restoring to life those who have lain more than an hour in a state of infenfibility.

The recovery is always attempted, and often effected, in this manner. They carry the patient immediately out of doors, and lay him upon the snow, with nothing on him but a fhirt and linen drawers. His ftomach and temples are then well rubbed with snow, and cold water, or milk is poured down his throat. This friction is continued with fresh snow until the livid hue, which the body had when brought out, is changed to its natural colour, and life renewed; then they cure the violent head-ach which remains by binding on the forehead a cataplafm. of black rye bread, and vinegar.

In this manner the unfortunate man is perfectly restored, without blowing up the lungs, as is necessary in the cafe of drowned perfons; on the contrary, they begin to play of themselves fo foon as the furcharge of phlogifton makes its efcape from the body.

It is well worthy of obfervation, how diametrically · oppofite the modes are of restoring to life, those who are deprived of it by water, and thofe who have loft it by the fumes of charcoal: the one confifting in the internal and external application of heat, and the other in that of cold. It may be alledged, that the stimulus of the cold" produces heat, and the fact feems to be confirmed by the Ruffian method of restoring circulation in a frozen

limb

limb by means of friction with fnow. But what is fingular in the cafe of people apparently deprived of life in the manner treated of is, that the body is much warmer when brought out of the room than at the instant life is reftored, and that they awake cold and shivering. The colour of the body is also changed from a livid red to its natural complexion, which, together with fome other circumstances, would almost lead one to suspect, that they are restored to life by the fnow and cold water fome how or other freeing them from the load of phlogiston with which the system seems to be replete; for although the first application of cold water to the human body produces heat, yet, if often repeated in a very cold atmosphere, it then cools instead of continuing to heat, juft as the cold bath does when a perfon remains too long in it.

In short, I think it is altogether a curious fubject, whether you take into confideration the mode of action of the principle emitted by burning charcoal, and our phlogisticated crust; or the operation of the fnow and cold water. However, I fhall by no means take upon me to decide, whether the dangerous fymptoms related above are produced by the air in the room being fo faturated with phlogiston as to be unable to take up the proper quantity from the lungs, which occafions a furcharge in the system, according to your theory, or whe

ther fo fubtle a fluid may fomehow find its way into the circulation, and thereby arreft the vital powers; nor fhall I determine whether the livid hue of the body when brought out is changed into a paler colour by the atmosphere somehow or other absorbing and freeing the blood from the colouring principle, as you have shewn to be the case with blood out of the body: thefe are curious inquiries that I fhall leave to your investigation. I have only endeavoured to collect facts from a number of natives who have met with this accident themselves, or have affisted in restoring others to life. It is fo common a cafe here that it is perfectly familiar to them, and they never call in medical affiftance.

XXIII. An Account of an Apparatus applied to the equatorial Inftrument for correcting the Errors arifing from the Refraction in Altitude. By Mr. Peter Dollond, Optician; communicated by the Aftronomer Royal,

1..

T

Read March 4, 1779.

HE refraction of the atmosphere occafions the stars or planets to appear higher above the horizon than they really are; therefore, a correction for this refraction fhould be made in a vertical direction to the horizon.

The equatorial inftrument is so constructed, that the correction cannot be made by the arches or circles which compofe it when the ftar, &c. is in any other vertical arch except that of the meridian, because the declination arch is never in a vertical pofition but when the telescope is in the plane of the meridian.

To correct this error, a method of moving the eyetube which contains the wires of the telescope in a vertical direction to the horizon has been practised; but as the eye-tube is obliged to be turned round in order to