>72 PEGP.EE5 OF FACILITY WITH WHICH BODIES 



Pendulums of There is no need of much inveftigation to difcover the mode 



Crofthwaitc and f joing this; as either the pendulum invented by Mr. 

 Crofthwaite, of Dublin, or that contrived by Mr. Pine, will 

 fully anfvver this purpofe, though they will by no means per- 

 form that for which they were intended,— of effecting a com- 

 penfation of themfelves, in the manner of the gridiron pen- 

 dulum. 



Their miftake. The error of thefe gentlemen, in this refpect, is very fully 

 pointed out in a paper figned A. B. publiflied in the feventh 

 Volume of the Repertory of Arts, which would have been 

 much more creditable to its author,- had he not triumphed fo 

 much in his fuperior penetration on the occafion, which has 

 led him to forget himfelf fo far as to defcend to the illiberally 

 of national reflection on the part of Mr. (Jrofthwaife : for 

 which reafon I own I am happy to have it in my power to give 

 thefe gentlemen the fatisfaclion of feeing an error pointed out 

 in his paper in return ; which is, where he aflerts that a fmall 

 rod of mahogany muff, have the fame contraction and dilation, 

 from change of heat, as a folid plank of the fame wood, or 

 words to that effect, the fallacy of which opinion appears 

 from what has been here laid down : It would be eafy to dif- 

 tinguilh this philofophy by an appellation of' the fame flamp 

 as that which A. B. has bellowed on Mr. Crofihwaile's in- 

 vention, and the more unfortunately for his insinuation on 

 this occafion, as the Irilh method happens lo be the beft of 

 the two ; for Mr. Crofthwaite fupported his pendulum by a 

 folid wall, which would be much lefs affected by change of 

 heat in the air than the back of the clock-cafe to which Mr. 

 Pine attached his. 



Ufeofalarge The beft method of applying the foregoing facls to the 



block of ftone regulation of clocks appears to me to be, to procure a large 



for fixing a pen- ° r 



dulum and clock, cylinder, or octagonal prilm, of (tone, (he diameter of whole 



bafe is equal to its height, and exceeds the length of the pen- 

 dulum by fome inches at lead, and as much larger as it could 

 be got the better: one of a cubic (liape would alio do, if its 

 mafs of matter exceeded that which could be got of the other 

 forms ; for this purpofe granite ftone feems preferable, and in 

 the next place Portland (tone, as Ihey can be eafily had in 

 large blocks ; but it is probable that (tones which grow damp 

 in moid weather would not be fo proper for this purpofe. To 

 this block of flone a pendulum fliould be attached with a (ingle 



compen fating 



