MODIFIED ly COMPRESSION. 147 
placing a heavy mafs, (fig. 40.), fo as to act direfly and 
fimply upon the muzzle of the barrel; this mafs being guided 
and commanded by means of a powerful lever, (a4). For 
this purpofe, I procured an iron roller, weighing 3.cwt. 7 lb., 
and fufpended it over the furnace, to the end of a beam of 
wood, refting on a fupport near the furnace, with a long arm 
guided by a rope (¢¢) and pulley (d), by wach the weight 
could be raifed or let down at plehfure. 
Wiru this apparatus I made fome tolerable experiments ; but 
I found the weight too light to afford certain and fteady refults 
of the beft quality. I therefore procured at the foundry a 
large mafs of iron (f), intended, I believe, for driving piles, and 
which, after allowing for the counterpoife of the beam, gave a 
direct preflure of 8.1 cwt.; and I could, at pleafure, diminith 
the comprefling force, by placing a bucket (¢) at the extremity 
of the lever, into which I introduced weights, whofe effeé& 
on the ultimate great mafs, was known by trial. Many _bar- 
rels failed in thefe trials: at laft, I obtained one of {mall bore, 
inch 0.54, which gaye two good refults on the 22d of June 
E8O4sihp de 
No. 8. Dror c to afcertain the leaft comprefling force by 
which the carbonate could be effectually conftrained in melt- 
ing heats, I firft obferved every thing ftanding firm in a heat 
of above 20°; I then gyadually threw weights into the bucket, 
till the.comprefling force was reduced, to 2 cwt. Till then, 
things continued fteady ; but, on the preflure being ftill further 
diminifhed, metal began to ooze out at the muzzle, with in- 
creafing rapidity. When the preflure was reduced to 14 cwt. 
air rufhed out with a hifling noife. I then {topped the experi- 
ment, by pouring water on the barrel. The piece of chalk 
‘had loft 12 per cent. It was white and foft on the outfide, but 
firm and good in the heart. 
T2 rm § ONO» Os 
