154> History of Mechanical Inventions, fyc. 



The rotatory gas-burner, which is represented in Plate I. Fig. 25, is 

 the invention of Mr Nimmo, brass-founder in Edinburgh. It displays 

 great ingenuity, and revolves by the reaction of gas issuing at the ordinary 

 pressure. In the section shown in the figure PQR is the gas tube communi- 

 cating by its lower end PQ, with any gas pipe. This tube, which is conical 

 at its upper end R, terminates in a sharp pivot at R, and has several large 

 holes a made in it near the top, so as to allow the gas to escape. On the 

 outside of the tube PQR, and fixed to it at PQ, is the water tube ABCDPQ, 

 which is filled with water. These parts of the burner are all stationary. 



The revolving part consists of two horizontal tubes, crossing one ano- 

 ther at right angles. Only one of these tubes, EF, is seen in the section. 

 These tubes communicate with the vertical tube GHMN, the lower end 

 of which, MN, is open, and is immersed in the water tube ABCD, the 

 whole resting upon the pivot below R, and revolving upon it as a centre. 

 This revolution is effected in the following manner : The gas ascending 

 the tube PQR, escapes through the openings in it at a ; and being pre- 

 vented by the water within the tube GHMN, from getting out at its open 

 end MN, it fills the tubes EF, and issuing at the holes h k, at their ex- 

 tremities, its reaction upon the opposite sides of the tube produces a ho- 

 rizontal rotatory motion, the vertical tube GHMN, revolving freely in the 

 water, in the tube ABCD. 



If the contrivance now described, formed merely an elegant addition to 

 our gas-light apparatus, it would even, in this point of view, possess con- 

 siderable interest ; but there is reason to think, that, by a proper adjust- 

 ment of the velocity of rotation to the quantity of gas discharged, the 

 flame may be supplied with the requisite quantity of air, more perfectly 

 than can be done in a stationary burner. If this shall turn out to be the 

 case, the rotatory gas-burner may be the most economical contrivance for 

 burning gas. 



3. Curious Law respecting the Vibration of Pendulums. 



The very curious law, of which we propose to give a brief notice, has 

 been discovered by Davies Gilbert, Esq. M. P. and explained in the Quar- 

 terly Journal. 



As it appears from a very simple calculation, that every inch of variation 

 in the barometer must change about two-tenths of a second the daily 

 rate of a clock with a brass pendulum, in so far as buoyancy is alone con- 

 cerned, Mr D. Gilbert requested Mr Pond and Dr Brinkley to observe the 

 rates of their clocks, when the barometer was at its maximum and minimum 

 height ; and he learned with great surprise, that no variation could be ob- 

 served. 



Upon reconsidering the subject, however, it occurred to Mr D. Gilbert, 

 that the acceleration of the time of vibration produced indirectly by an 

 increased resistance, in consequence of reducing the arc of vibration, and 

 the circular excess, might be a perceptible quantity. This had not escaped 

 Mr Gilbert's notice, but he had regarded it as comparatively an evanes- 

 cent quantity. When submitting it to calculation, however, he found 



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