196 Mi f cellanea Curio fa . 



An Experiment of the Refrattion 

 of the Air made at the Com- 

 mand of the Royal Society, 

 March a8. 1699. 



By J. Lo.wthorp, A. M. 



WE took a Cylinder of Caft-Brafs 

 330 AB.CD, and cut one end of 

 it CD perpendicular to the Axis ax 7 the 

 other end AB enclin'd to it at an Angle of 

 about 27 0 . 30'. and therefore the Perpendi- 

 cular to this enclining plain, fc 9 and,the Axis 

 of the Cylinder ax comprehended an Angle 

 pea of about 620. $od. Tbefe ends were 

 groun'd very true upon a Glafs-Grinder's 

 Brafs-Tool, and each of them was compaft 

 about with a narrow Ferule of thin Brafs bbbk 

 Into the upper tide of the Cylinder at E was 

 folder'd the Brafs-Pipe EF, and into the un- 

 der tide at 6 the other Brafs-Pipe GH *, the 

 former of thefe Pipes being about 3 Inches 

 long, and the latter 6 Inches. Upon the 

 Plate ddd were fixt to two other Plates LL 

 perpendicular to it and parallel to each other. 

 Each of thefe two Plates had an Arch of a 

 Circle (equal to the. Circumference 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 Cy- 

 linder fell into the Arches; and being fa- 

 flen'd there with Socler, the Axis ax laid pa- 

 rallel to the Tte'tQ.ddd and about an Inch and 



half 



