454 Powers of Electro- Magnetism, Steam, and Horses. 



Dr. Scoresby in his " Magnetical Investigations/' that steel 

 magnets on his construction may be employed in the stationary 

 part of the electro-magnetic engine with much greater advan- 

 tage than electro-magnets. We have already adverted to the 

 imperfect construction of the magnetic apparatus employed 

 in the above experiments; had we employed one of equal 

 weight, but constructed of thin plates of hardened steel, and 

 furnished with armatures and batteries in proportion, we 

 think it highly probable that a power equal to that of one 

 horse might have been attained, the whole weight of the ap- 

 paratus being considerably under half a ton. 



Having thus determined the capabilities of electro-magne- 

 tism as a first mover of machinery, it will be interesting and 

 instructive to compare it with two other sources of power, viz. 

 steam and horses. 



1. A grain of coal produces, by combustion, sufficient heat 

 to raise the temperature of a lb. of water 1°'634. In other 

 words, we may say that the vis viva developed by the combus- 

 tion of a grain of coal is equal to raise a weight of 1335 lbs. 

 to the height of one foot. Now the best Cornish steam-engines 

 raise 143 lbs. per grain of coal; whence it appears that the 

 steam-engine in its most improved state is not able to deve- 

 lope much more than y^th of the vis viva due to the combus- 

 tion of coal into useful power, the remaining T 9 y ths being given 

 off in the form of heat. 



2. A horse, when its power is advantageously applied, is 

 able to raise a weight of 24.000,000 lbs. to the height of one 

 foot per day. In the same time (24 hours) he will consume 

 12 lbs. of hay and 12 lbs. of corn*. He is therefore able to 

 raise 143 lbs. by the consumption of one grain of the mixed 

 food. From our own experiments on the combustion of a 

 mixture of hay and corn in oxygen gas, we find that each grain 

 of food, consisting of equal parts of undried hay and corn, is 

 able to give 0, 682 to a lb. of water, a quantity of heat equi- 

 valent to the raising of a weight of 557 lbs. to the height of a 

 foot. Whence it appears, that one quarter of the whole 

 amount of vis viva generated by the combustion of food in the 



* We have been kindly informed by Mr. J. V. Gibson of Manchester, 

 an eminent veterinary surgeon, that 14 lbs. of hay and 10 lbs. of corn is the 

 average provender requisite to support a horse of average size, so as to en- 

 able him to work daily without any depreciation of his physical condition. 

 We have however equalized the quantities of hay and corn, on account of 

 the experiments on combustion having been made with a mixture contain- 

 ing equal portions. 



