r 766 j 
pendlcular thereto. The radius of the quadrant, 
which was divided into degrees, was two lines more 
than a foot and half in length. And here mull: be 
added an account of the other part of the apparatus, 
which was to communicate the eledfricity to the 
gnomon during a thunder-ftorm. Through a glafs 
bottle, the bottom of which was perforated, patted 
an iron rod, which was kept in its place, by means 
of a cork fitted to the mouth of this bottle, through 
which cork likewife was inferted the iron rod. A tile 
was removed from the top of the houfe; and upon 
this opening was placed the bottle, fupported by the 
neighbouring tiles, in fuch manner that one end of the 
iron rod was not only four or five feet above the top 
of the houfe; but the other end, which came through 
the bottom of the bottle, did no-where touch the 
tiles, or any other part of the houfe. To this end 
of the iron rod was fattened an iron chain, which 
was conducted into the chamber of Profeflor Rich- 
man, upon eledtrics per fe, fo as no-where to touch 
the building. The entrance to this chamber faced 
the north ; and at the fouth end of it there was a 
window, near which ttood a table four feet in 
height. Upon this the ProfefTor placed his eledtrical 
gnomon, and connected it with the chain, which 
was brought under the ceiling of the room over this 
table, and communicated with the apparatus on the 
top of the houfe, by means of a wire B C, which 
hung from the chain, and was joined there to A B , 
by the little ring £, and communicated with the rod 
D C at C. When the iron rod at the top of the 
houfe was attested by the thunder, or otherwife fuit- 
able condition of the atmofphere, the thread before- 
mentioned deviated from the perpendicular ; as it 
2 would 
