116 Mr. Baily's Experiments with the Torsion-rod 



so likely to be disturbed : and, having closed up the door, he 

 adopted Cavendish's plan of observing the motions of the tor- 

 sion-rod, on the outside. But, even in a situation like this, 

 we must not expect a constant uniformity of temperature for 

 a long period. Neither of these authors, however, has given 

 any information on this subject ; both of them, however, met 

 with anomalies for which they could not satisfactorily account : 

 and, although Cavendish suspected the cause of some of those 

 anomalies, yet he does not appear to have applied any remedy 

 for the evil, in any of his subsequent experiments. 



Mr. Baily remarks, that his first experiments were tolerably 

 regular, although the results were generally greater than those 

 obtained either by Cavendish or Reich ; but that he soon ob- 

 served discrepancies which convinced him that some disturb- 

 ing force was in operation, which he had not yet contem- 

 plated, and which he sould not discover. One of the most 

 striking evidences of such anomaly was the remarkable circum- 

 stance, that the arc of vibration, during one and the same ex- 

 periment, would seldom decrease in the regular manner which 

 it ought to pursue, if the torsion-rod were guided by an uni- 

 foi-m influence ; and moreover, that in fact it would frequently 

 z'wcrease, contrary to all the known laws of bodies so circum- 

 stanced. Notwithstanding these interruptions, he not only 

 considered it proper to continue the experiments, for some 

 time, in the usual manner, in the hope that he might thereby 

 eventually throw some light on the probable cause of the 

 anomalies, and perhaps be enabled to apply a correction for 

 the effect of their influence; but also was induced to institute 

 several new courses of experiments, as circumstances and sug- 

 gestions occurred, for the express purpose of elucidating the 

 subject. The theories of electricity, magnetism, temperature, 

 and currents of air— the influence of different modes of sus- 

 pension by single and double wires and by double silk lines 

 — the trial of balls composed of different substances and mag- 

 nitudes — were successively and frequently appealed to, and 

 various experiments made to discover their probable effect on 

 the results. The mode of conducting the experiments was 

 also varied in different ways, with a view of eliciting informa- 

 tion on the point in question. Some of them were carried on 

 like those of Cavendish, and others like those of Reich (for the 

 methods of these two experimentalists were very different from 

 each other), whilst many more were conducted on a plan es- 

 sentially different from either of them. Heated balls and 

 powerful lamps were occasionally applied near the torsion- 

 box, with a view to raise an artificial temperature, and thus 

 create a powerful influence ; and, on the other hand, masses 



