Mathematics and General Physics. 363 



ing the poles, which moving a crank turns a wheel and any ma- 

 chinery connected with it. The inventor has succeeded in thus 

 getting a moving power nearly equivalent to the lifting power 

 of the magnet. The main peculiarities may be thus stated :-— 

 1st, The reversing apparatus easily applied, without almost 

 sensibly altering its weight, to any number of electro-magnets. 

 %d, The connexion of the reversing apparatus with the vibra- 

 ting bar. 3d, The direct application of the entire, or nearly 

 the entire, lifting power to machinery. 4th, The action of se- 

 veral electro-magnets, without their interfering with each other. 



17. Mr R. W. Fox on a new Dipping Needle. The instru- 

 ment which shews, at once, the dip, intensity, and variation, 

 was exhibited. It contains graduated circles, moving in altitude 

 and azimuth, and a vertical index adjusted to the meridian, turn- 

 ing in azimuth till the needle is vertical. Hence the dip may be 

 deduced, and the intensity, by comparing the effect of a small 

 magnet, introduced. 



Professors Stevelly and Lloyd made some remarks. The ac- 

 curacy of the instrument was confirmed by the testimony of Sir 

 John Franklin, who had examined it in connexion with Messrs 

 Christie and Barlow, even under extreme conditions. 



18. Professor Hamilton on the theory of Logologues, and 

 other numbers of higher orders. He discussed the nature of al- 

 gebra, and whether it is to be considered a science, or only a 

 language ? His leading idea is, that it may be regarded as the 

 science of pure and abstract time, as geometry is the science of 

 pure space ; and that the distinction of positive and negative 

 corresponds to past and future. He regards imaginary quanti- 

 ties as couples of moments, or couples of steps : a given moment 

 as having a given position, in regard to time, as a given point 

 in space : each step has direction and magnitude. He referred 

 to his paper in the Irish Transactions, which contained his sug- 

 gestions for certain improvements and simplifications in algebra. 



Thursday, 13th August. — 19. Mr R. Roberts exhibited an 

 apparatus by which figures may be seen, or sentences read, as dis- 

 tinctly when revolving at a high velocity, as when in a state of 

 quiescence. It illustrates, also, the duration of light on the 

 eye. 



