od 
xy 
= 
— 
NATURAL 
eafily ; and watched this fhell for 
upwards of three hours, going into 
the houfe at intervals to warm my- 
felf. The lait time I went in was 
about half an hour after twelve, 
when, after a few minutes, I heard 
a fort of hiffing found, upon which 
running out, the plug was gone, 
and a cylinder of ice thot up, ex- 
ceeding any of the former, being 
62 inches high. Plug Jott. 
‘Dec. 24.—-A fimilar plug to the 
laft. I watched this with more 
fuccefs; for although abfent at in- 
tervals; yet at half paft four in 
the afternoon (therm. at 6°) I faw 
the plug fuddenly forced out by the 
column of ice, accompanied by the 
hiffing noife ; and obferving its fall, 
I found it at 62 feet from the fhell. 
The icy cylinder was 4 inches 
high, and the fuze-axis of the fheli 
I found jay nearly at an angle of 
80° with the horizon.. 
31.—Concluding from the fore- 
going experiments, that no plug 
could be fo-fixed, as to render the 
refiftance at the fuze-hole greater 
than at the weakeft part of the fhell, 
in which cafe I fuppofed it would 
_ burft (which was the primary ob- 
ject in thefe experiments) I thought 
it might be worth while to obferve 
how far the force of congelation 
would project a plug of a given 
‘Weight and figure, and forced in 
of the fledge-hammer. 
‘with the fame number of ftrokes 
For this 
purpofe, I placed the fuze-axis of 
the fhell at an angle of 45° with 
the horizon, and on the 31ft of 
December 1784, being the coldeft 
day of this year, the plug was pro- 
jected whilft I was abfent, a cylin- 
der was fhot out, in the direction of 
the axis, of 7% inches, and not in- 
_ ¢lining inthe leaft from that direétion 
to the horizon. The plug was lott. 
HISTORY. 
73 
Jan. 2, 1785.—Being colder than 
31ft December, in order to haften 
the effect, I put a mixture of com- 
mon falt and fal ammoniac to the 
water, and tied a long pack-thread, 
with a piece of red rag at its end, 
to the fuze, in order to find where 
it fell in the fhow. This plug 
made its efcape, like the reft; for 
at half paft fix it was flown, and a 
cylinder of 82 inches of ice ftand- 
ing over the fuze-hole. The plug 
was loft; for the red rag appeared 
no where on the furface of the 
{now. 
4.—Tried a plug made with 
fprings, in the manner of a fearcher, 
only very fhort and ftrong. Added 
the freezing mixture. The {hell 
gave a fudden crack at a quarter 
after nine, and inftantly fhot from 
its furface two thin plates of ice, 
refembling fins, about 2 inches in 
the higheft parts. On examining 
the fhell I found it burft, and the 
plug forced up about half an inch; 
and, on breaking the thell, the 
fprings were confiderably bent, fo 
as not to have recovered their fir 
fituation. 
g.— Repeated thelaft experiment, 
with a fimilar plug and the freezing 
mixture. It was thrown out, as 
before, and the projecting icy cy- 
linder was 33 inches high. 
Similar experiments were after- 
wards made with all the lefler fhella ; 
yet, though one or more of each 
fort were actually burft, more plugs 
were projected than produced that 
effect. -As foon as the fnow began 
to difappear from the furface, I 
fearched carefully for the plugs, and 
found fix of them; which, being all 
marked with notches afer the firtt 
experiment, I eafily tormed from 
them the foregoing table. 
Such was the refult of thefe ex- 
periments, 
