( Si0 ) 
PHILOSOPHICAL 
TRANSACTIONS. 
For the Month ot October^ 1699. 
The CONTENTS. 
I. Experiment of the Refra^ion of the Air made at the Command of the 
Royal Society, Mir. 2S. 1699. J. Lowthorp. A. M. 
II. yinExtraB of tV!>o Letters, from Dr. John Wallis, {Pr of effor ef Geometry in^ 
Oxford. ) The One to his Grace the Lord Archbijhop of Canterbury. Thg. 
Other to the Lord Bijlop of Worcefler. 
ni. The Report made by the Lord Treafurer Burleigk to the Lords of the Council y 
efthe Qonfultation had, and tpje Examination of the V lain and Brief Difcourjg 
hy John Dts far the il^een's Majefly. 25 Martii 1582. 
IV. Reflexions made on the foregoing Paper by M^-. John Greaves, Savilian- 
Vrofeffor of Aftronomy in the Uni-ver(ity of Oxford. 1645. 
\ • AnMly^teGometricayfi'venova 'vera MethodusRefolvendi, tarn Vroblemata Geo- 
fnetrica, qi{a7n Arithmeticas ^aflionss. ?ars prima, de Planis ; Authore D, 
Antonio Hugone de Omerique Sanlncarenfe.Sold by Sam. Snaith *;;^^Ben}. Wal- 
ford at the Princ^*s inSt. Pauls Church-yard London. 
E Experiment of the Refr^^ion of the Air made at the Command' 
of the Roy 4l6ocinji^M^r. 28, 1^9^ Bj J. Lowthorp. A. M. 
WE took a Cylinder ofCaft Brafs Fig. L ABCD? and cut 
one end of it CD perpendicular to the Axis ax, the 
other end AB cnclin'd to it at an Angle of about 27« 30^ 
and therefore the Perpendicular to this cnclining plairj> pc,. 
and the Axis of the Cvlinder ax comprehended an Angle p&a 
of about 62a. Thefc ends were groun*d very true upon - 
a Glaft-Grindcr's Brafs. Tool> and each of •'hem wascompaft' ^ 
about with a narrow Feru!e of thin Brafs thbk Into the upper ; 
fide of the Cylinder at E was folder'd the Brafs pipe EF^ and 
into the under fide at 6 the other Brafs pipe GH f the 
former of thefe Pipes being about 3 inches long, and the late 6 
inches. Upon the plate ddd were fixt two other plates LL . 
Perpendicular to it and paralle! to each other. Each of thefe 
twopiates had an Arch of a Circle ( equal to the Circumfe- 
rence of the Cylinder)' cut out of , its upper Edge^ fo that:; 
when the pipe GH was let through a hole near the middle of 
the plate ddd^ the Cylinder fell into the Arches 1 and being 
Ece , faftea'd \ 
