ON THE CONDUCTION OF HEAT. 



23 



utterly unable to draw any conclusion from these experiments. We shall 

 experience the same difficulty if we proceed to examine the other results in 

 the same way. If we confined our attention to experiments (1.), (2.) and 

 (3.), we might conclude that all the formulae are correct ; if to (8.) and (9.), 

 we should certainly conclude that all are incorrect. Nor is it easy to say 

 which is the best from the former test, or which is the worst from the latter. 

 Seeing, then, that agreement with experiment is no test of truth, it is not too 

 much to argue that disagreement is no test of error. We must eliminate the 

 efiect of the air, or be provided with experiments in vacuo, before we can 

 form our conclusions, unless we can be furnished with experiments of a much 

 more searching character than these. 



2. It is hardly necessaiy to call attention to the insufficiency of the class 

 of experiments which was made by M. Fourier, and of which we have exhi- 

 bited one specimen. The results for the ring, it is true, are not so obvious 

 that they might be deduced from popular reasoning, and we must give M. 

 Fourier great crpdit for selecting these results in order to show the agree- 

 ment of his theory with experiment ; but as we are now in want of a means 

 of disproving rather tlian of establishing theories, we must look, for results of 

 a totally dift'erent character. We shall point out where such are to be found 

 by and by. 



3. We think we may consider that experiment (10.) shows the inaccuracy 

 of the first formula ; it fails, however, to give any preference to one of the 

 other three. The table of errors is as follows : 



*rhe maximum ratio of error to the whole temperature is 



I. -87, II. & HI. -35, IV. -25. 



It is needless to comment on these results. None of them are sufficiently 

 close to warrant any favourable conclusion, and the first is so wide, that, were 

 there no other reasons, we should on this account be disposed to reject the 

 corresponding formula, and with it the axioms on which it depends. 



We do not know that any other remarks are called for by a review of the 

 results of theory as contrasted with experiment. What, then, does the whole 

 amount to? We find that there are three distinct ways of theorizing, each 

 adopted, apparently, in accordance with the known laws of nature, but which 

 differ essentially from each other. We do not perceive that our existing ex- 

 periments bear with greater weight in establishing or in disproving any one 

 of them than it does in establishing or disproving the other two. Each is 

 confirmed by one experiment, each at variance with another. Are we to 

 account for this circumstance from the difiiculty of conducting the requisite 

 experiments, or are we not rather to attribute the anomaly to the little re- 

 gard which has of late years been paid to a certain class of subjects, and 

 especially to tlie one before us ? We are not aware that it has suggested itself 

 to any one experimental philosopher to examine into the laws of conduction. 

 Much labour, it is true, has been bestowed in examining the conductive pow- 

 ers of different substances, and to the results of experiments carried on with 

 this object we naturally look Avith the hope of extracting a law ; but, unfor- 

 tunately, the nature of the experiments we are presented with is not such as 



