Progress of Invention. 75 



deuce on the question. This was the disappearance of the spec- 

 trum of a star when occulted by the moon's limb. It appeared to 

 him that if the moon possessed an atmosphere, it should show itself 

 by producing absorption bands, and also by a gradual fading of the 

 spectrum instead of a sudden disappearance. He also thought that, 

 supposing an atmosphere highly charged with aqueous vapour, the 

 red rays would be least affected, and that end of the spectrum would 

 be last to go, while a clear but dense atmosphere would, by refrac- 

 tion, render the blue rays most persistent. He therefore, on the 

 4th instant, adjusted his spectrum apparatus on the. star e Piscium 

 about three minutes before its occultation. He could not speak 

 positively as to any extra lines being introduced by the moon's con- 

 tact, the air not being in good condition, but certainly no part of 

 the spectrum disappeared before the other, the obscuration occur- 

 ring not in the direction of the length of the spectrum, but of its 

 breadth, cutting off all the colours at the same time, and not by a 

 process of fading, but as if an opaque screen had been slowly intro- 

 duced, about two-tenths of a second being occupied in the occulta- 

 tion. This experiment, therefore, further corroborated the general 

 impression of the absence of any appreciable lunar atmosphere. 



PROGKESS OF INVENTION. 



Application of Compeessed Air to 'WEAViNG.-'-Every one that 

 has witnessed the process of weaving, by means of the power-loom, 

 must have remarked the stunning and most disagreeable noise by 

 which it is accompanied. The greater part of this is due to the 

 mechanism used for throwing the shuttle alternately from one side 

 to the other. In the hand-loom, the shuttle was thrown by the 

 hand of the weaver ; in the power-loom, invented in 1785, mechanism 

 more or less resembling the weaver's arm was introduced for the 

 purpose. A great velocity was thus obtained, but an intolerable din 

 was produced, and what was far worse, a deterioration of the textile 

 fabric, consequent on the great vibration communicated to the whole 

 room, and on the irregularity of the motion which is imparted to the 

 shuttle. There is a very great loss of power also, in consequence of 

 the force not being applied in the right direction. Besides all this 

 the mechanism which acts on the shuttle is extremely liable to get 

 out of order : the thread is frequently broken : and it is necessary to 

 use large quantities of oil, which, becoming heated by friction, causes 

 a very disagreeable smell and unwholesome atmosphere, and not 

 unfrequently escaping, injures the cloth. But a great change for 

 the better is now very likely to be introduced. Compressed air 

 has recently been adopted as the means of imparting motion to the 

 shuttle, which may then be made very much lighter. The advan- 

 tages derived from this arrangement are believed by many to be 

 numerous and considerable. As the force is applied exactly in 

 the direction in which it is required, there is a great saving 



