Royal Society. 409 
All Eapermcnt of the Rarefaction of the Air 5 by Mr. Low- 
thorp. Phil. Tranf. ]SJ° 257. P- 3 39. 
PLATE XI. Fig. 2. y\.r. Lcwth or p took a cylinder of 
caft-brafs ABCD, and cut one end CD perpendicular to 
the axis aa^y the other end AB inclined to it at an angle of 
about 27 dcg. 30 min. and therefore the perpendicular to this 
inclining plane />c, and the axis ac:^ comprehended an angle 
pea of about 6z deg. 50 min. both thefe ends were ground very 
true upon a glafs grinder's brafs-tool, and each of them was 
compared about with a narrow ferrel of thin brafs bbbb-j into 
the upper fide of the cylinder at E was foldered the brafs- 
pipe EF, and into the under fide at G, the other brafs-pipe 
GH, the former of thefe pipes being about three inches long 
and the latter fix inches; upon the plate ddd were fixed two 
other plates LL perpendicular to it, and parallel to each other 5 
each of thefe two plates had an arch of a circle, vyhofe dia- 
meter was equal to that of the cylinder, cut out of its proper 
edge; fo that when the pipe GH was let thro' a hole near the 
middle of the plate ddd, the cylinder fell into the arches, and 
being faftened there with folder, the axis acx lay parallel to the 
plate ddd, and about an inch and an half above it ; the perpen- 
dicular end of the cylinder DC was covered widi an objea- 
glafs of 7|- foot telefcope 00^ and the inclining end AB with a 
well- polif lied flat glafs jf, which was carefully chofen to tranf- 
mit the obje6l diftinft enough, notwithftanding its obliquity to 
the vifual rays ; the ferrels were filled with cement round about 
the edges of the glafles, which lay flat, and every where 
touched the fmooth ends of the cylinder, that they might 
firmly fupport the weight and preffure of the excluded air : 
Inftead of a ciftern, as in the Torricellian experiment, there 
was ufed the inverted fiphon of brafs MNO Fig. 5. foldered to 
the plate ggg ; one of the fides MN flood perpendicular to the 
plate ,^g^, and the other NO ir-lined to it, and was fup- 
ported near the upper end O with a fmall prop of brafs kk : 
The cylinder was then placed upon a table Fig. 4. which was 
well faftened to a firm floor; the pipe GH was let thro' a hole 
in the top of the table; and the plate ddd was nailed down to 
it ; the tube of the telefcope sss with the eyc-glafs in it, was 
applied to the objedl- glafs, and a hair fixed at jc, the common 
Focus of both gla{res,^in the axis of the cylinder contmued 
upon the floor ; under the cylinder was nailed the plate 
gg-^ with the inverted fiphon upon it, and M was joined to H 
Vol. IIL Fff by 
