ZZ 'Experiments refpecling Heat. 



below, the phenomena will be the better obferved. The 

 wire being prepared by coiling it up into a fpiral, like a cork- 

 fcrew, inferring its fuperior extremity into a cork or cover, 

 adapted to the fuperior aperture of the receiver, and winding 

 a little cotton round its lower extremity; the cotton is to be 

 very flight ly dipped in the melted tallow of a candle, and then 

 fet on fire. This gives fuch a degree of temperature to th6 

 wire as occafions it to take .fire when introduced into the gas, 

 which is done bv removing the cork or cover from the re- 

 ceiver and fubftituting that containing the wire at the mo- 

 ment of its ignition. 



The wire then begins to deflagrate, and little globules of 

 melted iron are formed at its extremity : each falling off in 

 fucceffion when it acquires a weight fufficient to detach it 

 from the remainder of the burning metal. One circum- 

 itance, which cannot fail to imprefs the mind ftrongly with 

 the intenfity of the heat produced in this experiment, is, that 

 many of thefe globules, though they mull: neeeffarily nrft 

 pafs through the water in the plate, are always found, even 

 when the water is two inches or upwards in depth within 

 the receiver, to have fufed the vitreous glazing completely 

 through, and to be fo ftronglv united with it, that they can- 

 not be afterwards feparated without detaching the glazing, 

 together with the femi-vitrefied and flag-like globule which 

 adheres to it. . 



Another effect, which may be produced at pleafurc, fur- 

 Ilifh.es, if poffible, a ftiil more convincing proof of the in- 

 tenfity of the heat. The drops of liquid iron generally ac- 

 quire the fize of a final] pea before they detach themfelves. 

 If the experimenter, watching the moment, give a quick 

 jerk to the wire, and make the globule flrike the fide of the 

 glafs, it will often be found to melt its way through in an 

 inftant, leaving a hole in the glafs, whofe edges are as well 

 defined as if it had been drilled. The glafs ufed on this- 

 occafion in the Society, and which is fuch a one as Mr. Var- 

 lev, the experimenter to this inftitution, makes ufe of in his 

 public lectures, is generally as thick as a ftrong drinking 

 tumbler j and it is worthy of remark, that, though in charg- 

 ing the glafs, perhaps not a minute before the experiment, 



it 



