6l6 PHILOSOPHICAL TRANSACTIONS. [aNNO 17 10. 



at all, in the air; nor such a degree of heat, able to strike any injurious, or suf- 

 focating effluvia, out of the metalline particles. 



Some other Experiments on the foregoing Head. — ^The passing of air through 

 a red-hot glass tube into an exhausted receiver, had no manner of influence on 

 a sparrow put into the same ; but on passing air through red-hot charcoal, be- 

 fore it entered the tube that conveyed it into the exhausted receiver, the animal, 

 in that medium, in about a quarter of a minute, gave signs of presently expiring; 

 but being taken out at the same time, it recovered, and continued living and 

 well for some days after. Yet it was concluded, had the bird's continuance in 

 the receiver been but double that time, her recovery would have been very 

 doubtful. I have likewise tried air passed through the flames of spirit of wine 

 and oil of turpentine; the effect was much the same as to the spirit of wine, 

 the flame of a candle being immediately extinguished when plunged into it; but 

 the air which passed through the flame of the oil of turpentine, took some 

 unctuous fumes along with it into the exhausted receiver; which fumes on the 

 near approach of a lighted candle, suddenly took fire, and continued to burn 

 on the upper surface till they were stifled by covering close the receiver. And 

 on several repetitions, it answered much the same, till the whole quantity of 

 fume was consumed. 



A Description of the Apparatus for making Experiments on the Refractions of 

 Fluids. With a Table of the Specific Gravities, Angles of Observations^ and 

 Ratio of Refractions of several Fluids. By Mr. Fr. Hauksbee, F. R. S. 

 N° 328, p. 204. 



The whole apparatus is fixed on a table, parallel to its surface. On one and 

 the same axis is fixed a sextant, of 4 feet radius, and a moving limb to bear the 

 object. The sextant is divided into degrees and minutes by a diagonal, and 

 remains always fixed. The object, which is placed on the moving limb, is seen 

 parallel with the table when observed through the prism, and at no degrees on 

 the sextant; but when any transparent liquid is put into the same, the object 

 must be elevated till it appears to the eye; then observing how many degrees 

 and minutes the index on the limb cuts on the sextant, we note it, and call it 

 the angle of observation. Thus for different liquids we have different eleva- 

 tions of the object, as in the following table. The sight slit is composed of 

 two pieces of box wood, planed parallel to each other; these pieces are sepa- 

 rated only by three slender slips of common cards, and with that intervention 

 are screwed down one upon the other, exactly parallel with the axis of the 

 moving leg and sextant. The prism, through which it directs the sight, is 

 placed pretty near it, and consists of an angle of 44° 54', which angle is fixed 

 perpendicular to the plane of the table, its upper side being parallel with the 



