2l4 FERPETVAL MOTION, AND JOINTED PARALLEL RULE. 



them with thefe remarks. Very defirous of avoiding every fpe- 

 cie^ of altercation, I have hitherto cautioufly abftained from 

 •ngaging in literary difputes; and I ftiall moil certainly endea- 

 vour to avoid them in future. 



I am refponfible to the public for the accuracy of the accounts 

 ^hich I have publiQied of my experiments j but it cannot rea- 

 fonably be expeded, that I fliould anfwer all the obje6lions that 

 may be made to the conclufions which I have drawn from them. 

 It will however, at all limes, afford me real fatisfaction to fee 

 my opinions examined, and my miftakes correded; for ray firlt 

 and mod earned with is, to contribute to tl?e advancement of 

 ufeful knowledge. , 



XVI. 



Account of two Sketches ; viz. one for a perpetual Motion, and 

 the other of a Jointed Parallel Rule, xvhich has no fide Deviation, 

 In a Letter from R. B, 



To Mr. NICHOLSON. 

 SIR, 



I 



Perpetual mo- JL was much gratified feveral years ago by fome effays with 

 in^e PhUofo- ^^^^^^ T^^ obliged your readers upon the perpetual motion. In 

 phical Journal, the firft volume, p. 375, of your quarto feries, I find an account of 

 feveral fchemes (neceflarily abortive) for producing perpetual 

 motions by the action of gravity, and in your third volume, I 

 find an account of various methods of keeping up the motion 

 of a machine by means of the changes which take place in the 

 barometer and thermometer, I have ventured to fend you the 

 iketch of a project for a perpetual motion of the latter kind, 

 which has long remained among my memorandums. You will 

 fee that it is not of the clafs of perpetual motions properly 

 fpeaking, but merely the application of fome exifting intermit- 

 tent motions in nature to the purpofe of maintaining the rotation 

 of machinery. If you (liould heiitate about inferting this, I 

 fchink the other (ketch which accompanies it of an ufeful in- 

 ftrument, cannot fail to meet your approbation. 

 Defcnptionof a Fig. I, Plate XII. A reprefcnts the marine barometer of 

 wheel kept in H^Hey, but varied by the addition of a veifel B at the open 



motion by the ..,, i n-j r rr . 



marine baromc- end, in which the water oi Other fluid, expoles a furface nearly 

 fier. equal 



