0?i a Netv Method of Illuminating Church Clocks, 293 



properties of variouis substances arises entirely from tliis clian»e in the 

 position of their component particles, effected either by the communica* 

 tion or abstraction of heat after solidification, there can be no doubt. 

 And these changes are applied to many very important purposes in the 

 arts and manufactures — such as the hardening and tempering of steel, 

 the rolling of commercial zinc, and rendering that metal permanently 

 malleable, the annealing of glass, and a variety of other uses, particularly 

 in crystallization, which might be adduced. 



The following experiments were made to ascertain to what extent the 

 emission of latent heat takes place. The melted alloy was poured, in a per- 

 fectly fluid state, on a bulb of a thermometer, placed in a small platinum 

 crucible, having a capacity equal to about 70 grain measures of water, and 

 standing in a vessel of cold water or mercury. The thermometer, sur- 

 rounded by the solidified metal and crucible, was removed from the cool- 

 ing medium before it had reached its stationary point, and the greatest 

 decrease of temperature noted. The heat then rose rapidly again, and 

 the maximum effect was registered. The fusing point of the alloy was 

 202** Fahrenlieit, and the following results were obtained : — 



Exper. Fahr. Fahr. Diff. Fahr. 



1 thermometer fell to 97® and then rose to 167* 60** 



2 94 149 66 



3 90 150 60 



4 87 147 CO 



6 104 156 62 



6 97 148 61 



7 92 152 CO 



8 104 155 61 



So that in four out of the eight trials, a difference of 60° Fahrenheit 

 was rendered apparent. 



In a platinum crucible of larger size, the effects were not so marked, 

 34** Fahrenheit being the greatest difference obtained ; this of course 

 would arise from the greater bulk of the melted metal not exposing com- 

 paratively so large a surface to the cooling medium. 



On a New Method of Illuminating Church Clocks, By Mr R. 

 Bryson, Edinburgh. (Communicated by the Royal Scot- 

 tish Society of Arts.*) 



The usual methods employed in the illuminating of church 

 clocks at night have hitherto been liable, first, to the objection 



♦ Read before the Royal Scottish Society of Arts 22d Nor. 184f. 



