hydrogen gas, by its combination (fcixture) 
vàth nitrogen may be hevier than thè pure 
hyàrogen gas, yet it liappens to b e much 
lighter thar atmospheric air.' Hence thè 
entrance of this (latter) air into thè \x6i^ 
ometer and its ccming into contact v/i th thè 
hydrogen gas, iriade a very slight mixture, 
or none at all, with it, and thè fosforus 
therefor reirains partly or entirely with- 
out light,* But if insted cf holding thè 
udioirieter upright (after) raising it from thè 
water, turiid it upside down, then thè hy- 
drogen gas remaining at thè bottcm was 
foro ed to thè top and driven out by thè 
ordinary air, whereupon thè re was a fresh 
exhibition cf thè light, 
Sec® 113: Ihese obserTations upon thè 
fosfcric wocds wer fcllowd by a few others 
iTiade thè fcllowing Septernber at Venice, up- 
on that large marine worm coniraonly cald 
Sepia of f icinal is ® (Ihis) dces not giv 
1 ifrht when alive, but cnly when actually 
putrescent* I was not abl e te exaniin a 
single specimen which gave light whii e a- 
live* When I placed a few small pieces in 
thè udiom:eter, I saw^ first that thè light 
was equally bright in sea-water and in thè 
air; second, that all of thè light becam.e 
dimlnisht by thè introduction of nitrogen; 
third, that by mdxing ordinary air with this 
gas (iNi) thè light v/as restord tc some ex- 
tent; forth, that thè light was dubly mor 
bright in cxygen than in coirjmon àir* fhese 
observations agree very remarkably v/ith ^ 
thcse recorded fcr thè fosfcric wcods* 
Sec* 114: Having been at thè seaside, I 
afterwards wisht to examin those fOvSforic 
but ded animai s which I had not been abl e 
to examin whil e alive, which inhabit those 
w'aters, amcng others, thè penna tuie and thè 
fosfcric medusaej but I was obliged to put 
alde that part o'f miy wish, not serching in 
