288 



Mr. W. H. Preece. 



[Dec. 22, 



Lead. 



Diameter of wire. 



Cui'rent in amperes. 



















Fusing 

 current 

 calculated 

 from the 

 formula 

 ad™. 



-Amperes. 



Constant 



In 



inches. 



In 



centi- 

 metres. 



Standard 

 wire 

 gauge 

 No. 



Shellac 

 flake 



melted 

 with. 



Wire 

 red hot. 

 Yisible 

 in air. 



Wire 

 fused. 



"a" 

 when 

 d ex- 

 pressed 

 in inches. 



o-oio 



'012 



025 

 -030 



33 

 30 



1 1 -666 



f 1 -825 

 1 



% 



1- 984 



# 



2- 461 



1- 984 



2- 341 

 2-659 

 2 -777 



| 1-990 

 | 2-616 



2339-5 

 21116 



0-014 

 0-018 

 0-020 

 0-026 

 0-030 



0-036 

 0-046 

 0-051 

 066 

 076 



2S 

 26 

 25 

 22 

 21 



|3 -095 



f 3 -016 



L ■• 



|3'810 



1 5 -471 

 j 6 -838 



# 



3- 016 



# 



3 '889 

 * 



4- 827 



# 



no redness 

 # 



no redness 



3- 095 



3 821 



4- 023 



4 - 383 

 4-907 

 4-927 

 7-000 



7- 000 



8- 366 

 8-850 



\ 3-296 

 J 



^ 4 "64.0 



X 5-430 

 J 



| 8'344 

 | 8-980 



2305 3 

 1811 "3 

 1712 -3 

 1668-5 

 1702 -1 



0-033 



0-084 



21 



6-526 





10 -93 



11-520 



1828-2 



0-036 



0-091 



20 



7-831 





12 -40 



13 120 



1814 -4 















Mean = 



1921 -5 



* Lead wire fuses without previously emitting light when a small shellac flake 

 touches the wire. 



Series II. 



The second series of experiments was made to determine the rela- 

 tive effect of the sudden application of powerful currents on wires of 

 different materials such as would occur if in practice a short circuit 

 suddenly took place. An electromotive force of 100 volts was used, 

 and there being no appreciable resistance in the external circuit but 

 the wire, the latter was subjected to the blow of a momentary current 

 of immense and immeasurable strength. 



