'Experiments and Obfervations. 597 
and nearly one inch thick, I pafted a piece of white pa- 
per, and delineated upon it a right-angled triangle egf, 
one lide gf of which came very near the edge cd of the 
board; the other fide ef, which hands perpendicular to 
GF, was divided into equal parts, reprefenting degrees of 
Fahrenheit’s thermometrical fcale. The lowed: of 
thofe degrees was near the freezing point, and the upper 
was not above the 1 1 o°, it being as much as I was in 
want of. From the point g right lines were drawn to all 
the degrees in the fcale ef, and many other right lines 
parallel to the fcale ef, and confequently perpendicular 
to the bafe gf, were drawn through the whole area of 
the triangle. Now when the thermometers were con- 
ftrudfed, I found, by comparifon with a ftandard thermo- 
meter, two points whatever, which I marked w r ith the 
file upon the tube, and by a note of thefe thermometers 
I knew to what degrees they anfwered. Thus, for in- 
ftance, upon the thermometer hl two marks were made, 
viz. I anfwering to the 40th degree, and k to the 70th 
degree. Now when this thermometer was to be ufed 
I placed it upon the board abcd with the tube parallel to 
the fcale ef, which could be eafily done by the help of 
the parallel lines drawn upon the triangle, the ball of the 
thermometer being out of the board; thus I Aid the 
thermometer backwards and forwards till the mark I, 
4 I % which 
