(20 4 ) 
'VI. A D-efcription of the Apparatus for making Ex- 
periments on the RefraHions of Fluids : With a 
Table of the Specific 4 Gravities, Angles of Obfer- 
V attorn j and Ratio of Refractions of feVer al Fluids . 
(By Mr Fra. Hauksbee, F. R. S. 
T HE whole Apparatus is fix’d on a Table, parallel 
to its Surface. On one and the fame Axis is fix’d 
a bextant, of a Radius of 4 Feet, and a moving Limb to 
bear the Objed. The Sextant is divided into Degrees 
and Minutes by a Diagonal, and remains always fixt. 
The Objed, which is plac’d on the moving Limb, is 
Teen parallel with the Table when obferv’d through the 
Prifm, and at no Degrees on the Sextant 5 but when any 
Transparent Liquid is put into the fame, the Objed muft 
be elevated till it appears to the Eye: Then oblerving 
how many Degres and Minutes the Index on the Limb 
cuts on the “Sextant, we note it, and call it the Angle of 
Obfervation. Thus for different Liquids you havo dif- 
ferent Elevations of the Objed, as you will find by the 
following Table. The Sight-Slit (if I may call it foj 
is compofed of two pieces of Box Wood, plan’d paral- 
lel to one another : Thefe Pieces ave feparared only by 
3 (lender Slips of common Cards ^ and with that Inter- 
vention are ferew’d down one upon the other, exadly 
parallel with the Axis of the moving Leg and Sextanr. 
The Prizm, thro' which it direds the Sight, is plac’d 
d. * 
pretty near if, andconfifts of an Angle of 44.54, which 
Angle is fix’d Perpendicular to the Plane of the Table, 
. % 
