[ i 4 6 ] 
XXIX. A Defcription of a new 'Thermometer 
and Barometer : In a Letter to the Right 
Honourable George Lari of Macclesfield, 
Prefident of the Royal Society , from Keane 
Fitzgerald, Efq\ F. R. S. 
My Lord, 
Read May 7, TT Took the liberty of addrefiing a paper 
X to your Lordlhip laft year, with an 
account of an inftrument, which was intended to 
anfwer, in fome meafure, the purpofes of a thermo- 
meter and pyrometer. The degrees the index had 
pointed to, during the abfence of an obferver, were 
marked by a pencil applied to it. But I found great 
inconvenience from the fridion of the pencil, which 
mud be fhong, or it does not mark diftindly ; be- 
lides the trouble of rubbing out the mark, every time 
a new obfervation was intended. 
I muff beg leave to trouble your Lordfiiip with 
the defeription of an inftrument on the fame prin- 
ciple, as a thermometer only, with regifters to mark 
the leaft variation that can happen during the abfence 
of an obferver, which are fet for any future obferva- 
tion, with the greateft eafe. As this inftrument is, 
in part, like the former, I /hall only mark the va- 
riations from it. 
The firft bar A is fixed at the upper end, by three 
ferews b , b , b , and joined at the lower end to the 
arm of the firft lever, by a pin c, which paftes 
through both. [Vide Lab. V.] 
2. The 
