Meafurement of a Safe on Hou n flow- Heath . 44.-/ 
are both reprefented in the plate, and only differ from 
each other in the fhape of the brafs milled-headed nut 
that work upon the fcrew, of about -a £ inches in lenpth, 
into which the right-hand end of each hook is formed* 
Thus, while the nut enters very freely into, and reffs upon, 
the fork, the left-hand end of the hook has a circular hole in 
it, whereby it flips eafily off and on of the brafs pillar. By 
referring to the plate, it will appear fufffeiently obvious, from 
the nature of the nut on the left-hand hook, that it could only 
move the rod on to coincidence, and could not bring it back 
again, if the bufinefs happened at any time to be overdone-; 
in which cafe it was neceffary to move the rod a little back- 
wards by the hand, and then to work anew with the nut,, 
until the coincidence was accurate : whereas the nut on the 
right-hand hook, having two (boulders, could either pufli or 
pull the rod forwards or backwards: and although this ap- 
peared to be an advantage, yet it was found from experience, 
that it rather bound the hook too much, and OccafiOned a kind 
of fpring in the parts, which fometimes diffurbed the coin- 
cidence 011 the removal of the hook ; wherefore it was often ap- 
plied, like the other, by placing the fcrew itfelf in the fork, 
and working with both fhoulaers of the nut behind it. 
The pofitions of the thermometers, and mahogany oval lid 
on the top of the cafe, have already been mentioned. This 
laft, being unlocked and removed, permits the cafe to be looked 
into, or the hand to be admitted, in order to be certain that 
the faftenings remain fafe and entire in the inf de. Brafs caps, 
with the refpeftive number of the rods engraved on them, are 
Mkewife ferewed on the male- fere ws in the ends of the cafe, 
through which the extremities of the tubes project, to pre- 
ferve them from accidents when not in ufe. And, laffly, to 
Vol, LXXV e Nan % ftrengthen 
"Xfj 
