MAYER 



279 



Since figures were already known for the quantity of heat 

 in question, and also for the change in volume at given pres- 

 sure, Mayer was able to calculate the equivalent by means of 

 an imaginary experiment, no actual fresh experiment being 

 necessary. Using the figures of that day he came fairly 

 close to our more accurate figure of to-day, 427 metre- 

 kilograms for one calorie. He also remarks that other 

 gases, according to the measurement, give the same value as 

 air, and that this is a confirmation of his view. Furthermore, 

 he himself arranged an experiment in which work was trans- 

 formed into heat, by measuring in a paper factory the rise in 

 temperature of the pulp, which was being stirred with the 

 expenditure of five horsepower; the resulting amount of 

 heat was found, when the losses were taken into account, to 

 agree with his equivalent.^ 



We see that Mayer produced altogether quite enough ex- 

 perimental basis. Apart from anything else, the experience 

 that perpetual motion was impossible, so often used for the 

 construction of important conclusions, comes in here with its 

 full weight; indeed, it occupies the central position of the 

 whole; it furnishes the assurance that an increase of energy 

 cannot take place in any known process. The apparent 

 fact, long regarded as true, that a loss of energy can actually 

 take place, as in the case of every system of frictional pro- 

 cesses, was proved by Mayer to be a delusion, for he showed 

 that in such cases there is a transformation into heat, which is 

 likewise a form of energy. With this, the complete in- 

 variability of the total sum of energy was made clear, and 

 hence it was above all necessary to clear up the processes 

 connected with heat, in order to arrive at an idea of the way 

 in which energy is concerned. This clarification was also 



objection. This statement ignored Gay-Lussac's discovery above- 

 mentioned, and Mayer's express reference to it. 



^ Mayer expressly stated that more exact experiments were needed; but 

 for his own person he regarded the continuance of his medical practice as 

 the more necessary. 



