[ 526 ] 
machine fhow figns of electricity ; and as thefe figns> 
when examined, appear to be different in the chain, 
and in the machine, and the globe having, as he 
fuppofes, drawn from the machine part of its natural 
or common quantity of electricity, and given it to 
the chain, he calls the eleCtricity appearing in the 
chain, eleCtricity by excefs 5 and the electricity ap- 
pearing in the machine, eleCtricity by defedi ; which 
anfwer to our terms of pofitive and negative eleCtri- 
city, or eleCtricity plus and minus . And thus his 
expredions, electrifying by the chain , and eleSiriJying 
by the machine , are to be underftood, electrifying po- 
fitively , and electrifying negatively . 
LI. An uncommon Cafe of an Hcemoptyfs \ 
hy Erafmus Darwin, M. D. 
To the very Honourable and Learned the Frefident , 
and Members of the Royal Society. 
Gentlemen, 
Rca( j5o ,43r ]pHE following cafe of a difchargc 
1 of blood from the pulmonary ar- 
tery, appears to have been owing to a caufe different 
from any mentioned amongfl the writers of medicine : 
and as, from the knowlege of that caufe, the cure, 
was fo eafily deduced, I flatter myfelf, you will not 
elteem it unworthy your attention. 
A gentleman, reflding near this place, between, 
forty and fifty years of age, of a pale and meagre 
habit, has been daily afflicted with violent head-achs 
for 
