446 Major-General Roy’s Account of the 
A brafs ftrap or bridle, about eight-tenths of an inch broach, 
paffes over the top of the cafe, and defcending down each fide, 
bends outwards, fo as to form a projection for the reception of 
the wheels, whofe pivots turn in, but near to the lower end 
of the bridle, which is kept in its place by means of the two 
fide fcrews working in grooves, and the milled-headed fcrew at 
top. This laid ferves likewife to raife or deprefs the wheels at 
pleafure. 
Each rod has two crofs feet, placed immediately behind 
their refpedtive pair of wheels, extending outwards about 4I 
inches from the center on each fide. Under their outward ex- 
tremities, fmall pieces of hardened fteel, formed into the teeth 
of a file, are fixed by means of fcrews. When the firft rod 
has been laid in its true place, by unferewing the milled heads, 
the wheels are buffered to rife ; whereby the whole weight is 
removed from them, and thrown upon the teeth of the files, 
which then indent themfelves into the furface of the ftand, 
and become as it were united to it. But when the fixed button 
of the fecond rod is brought to prefs againft the moveable but- 
ton of the firft, the weight being then thrown upon the 
wheels by ferewing the milled heads at top, the rod is eafily 
moved on by the following apparatus. 
The three rods are numbered, as were thofe of deal, 1.2; 3.4 ; 
5.6. On the firft or odd end of each rod 1. 3. and 5. there ftands 
a brafs fork, about two inches high, fixed by four fcrews and an 
oblong plate to the top of the cafe. On the fecond, or even 
end of each, 2. 4. and 6. there ftands a brafs pillar of the fame 
height with the fork, likewife fixed to the top of the cafe by 
four fcrews and a circular plate. Two fteels rods or hooks 
were indifferently ufed for bringing up the moveable rod (the 
weight then lying on the wheels) into its true place. They 
are 
