34 b Ah r . smeaton’s Fundamental Experiments 
paper, that the marks thereupon may be the more confpicuous. 
The crofs-piece II is made to project fo far before the 
pillar, that the bodies in their vibrations may pafs clear of ir, 
without danger of ftriking it ; and alfo the arch MN is brought 
lo far forward as to leave no more than a clearance, fufficient 
for the rods to vibrate freely without touching it. 
fig* 2. Shews one of the compound bodies, drawn of its 
full lize. AB is a block of wood, and about as much in 
breadth as it is reprefented in height, through a hole in which 
the wood rod CC pafles, and is fixed therein. 
DB reprefents a plate of lead about three-eighths of ah inch 
thick, one on each lide, fcrewed on by way of giving it a com- 
petent weight. d¥>efg reprefents the edge of a fpringing plate of 
brafs, rendered elaffic by hard hammering ; it is about five- 
eighths of an inch in breadth, and about one-twentieth of an 
inch thick. It is fixed down upon the wooden block at its end 
by means of a bridge plate, whole end is fhewn hi, and is 
lerewed down on each fide the fpring plate by a fcrews which 
being relaxed the fpring can be taken out at pleafure, and acf- 
jufted to its proper fituation. kl is a light thin Hip of a plate, 
whole under edge is cut into teeth like a fine law or ratchet, 
and is attached to the fpring by a pin at k, which p aides 
through it, and alfo through a fmall Hud ri vetted into the 
back part of the fpring, and upon which pin, as a center, it is 
freely moveable. 
inn fhews a fmall plate or Hud feen edgeways raifed upon die 
bridge plate, through an hole in which Hud the ratchet pafles ; 
and the lower part of the hole is cut to a tooth lhaped pro- 
perly to catch the teeth of the ratchet, and retain it together 
with the fpring at any degree to which it may be fuddenly 
bent ; and for this intent it is kept bearing gently downward, 
by means of a wire-fpring opq, which is in reality double, the 
bearing 
