Oxyggiie In tis JS/a^aWt of Fi/i — TLmnJoSiorm. jg . 



bhdJer of nni i and I was perhaps prevented from finding it out. by hearing Dr. Monro \n 

 his leaures fay, ,t was natural to fuppofe it fixed air. However, although this authority 

 prevented me from putting it to the tcft of experiment for fome time, yet one day, on our 

 ^oyage, havnig caught a very large fwovd-fia,, I collected the contents of ail the air-bladders- 

 for in that fifli the bladder appeared divided into innumerable cells, which had no commu- 

 n.cation with each other. They afforded fo much au that I coUeded a quart bottle full. 

 My furpnle was great to find that the gas contained was oxygene. A flame was bri-htened, 

 au Ignited ftick was made to re-kindle, and it was fo ilrong and pure, that the common ex- 

 periment of a piece of fteel wire, heated and put into it, fucceeded well, and threw cut a 

 mod vivid light when melting. I have committed to writing my thoughts on this fubjca 

 at greater length, and I wi(h to infer that this pure air is to lerve the purpofes of life when 

 the animal is far below the furface of the water." 



The preceding difcovery of oxygene is, I believe, perfeftly new. Dr. Prieftley, in his 

 Experiments in Natural Philofophy abridged and methodized, vol. ii. page 462, mentions 

 the commencement of a courfe of eicperiments on the ftate of the air which is contained in 

 the bladders of filhes. He remarks, that when thefe are taken out of the fifli, the air cannot 

 be got from them by preflure through any exifting aperture, but that he was always obliged 

 to cut or burft them. The firft time that it occurred to him to examine the air contained 

 in thefe bladders, he found it in a great number of them to be not at all afFeded by nitrous 

 air. But at another time he found air from the fame kind of fi(h, namely, roaches, to be 

 flightly affeded by that re-agent. It appears, therefore, from thefe trials, that he feldom 

 met with oxygene, and then in fmall quantity ; but what the other portion of air might 

 confill of was not afcertained by his experiments. 



Fourcroy afterwards made experiments on the air contained in the air-vefTel of the carp, 

 which, at certain feafons, he affirms, may be had very cheap and in abundance at Paris. It 

 was perfectly pure azotic gas, for the moft part, though fometimes it contained a fmall 

 quantity of carbonic acid gas. He thinks, from the nature of this fluid, that the air in the 

 bladders of fifces is produced in the ftomach. (Ann. dc Chim. I. 47.) The obfervations of 

 Dr. Brodbelt feem to render this general conclufion at leaft doubtful. 



VI. 



■ Account of certain remarkable Changes of Colour and DWeakn of the Clouds dur'wg a Thunder- 

 K Siorin. 



ii-MONG other circumftanccs enumerated by Dr. Priedley in the defcription of the clouds 

 in a thundcr-aorm, in his Hiftory of Eleflricity, mention is made of a certain luminous ap! 

 pearance, evidently independent of folar refleaion. I have always fuppofed this expreffion 

 to denote the opake whitenefs of the upper or arched outline of certain tliunder-clouds, con- 

 trafted with others apparently in contad with them, but of a dull leaden hue ; and accord 

 ingly I was difpofcd to conclude that the whole was nn optical delufion, arifin-r from tlie 

 pofition of tlie fpeftator, who imagined, though fallely, that tlie latter clouds were as 

 much expofed to the fun's dired light as the former. But the ftorm which happened oa 

 .Sunday morning, the 30th of July lad, exhibited fads which feem to H.ew that the tranfitio,, 

 of e cdricity may caufe the clouds to emit a fteady permanent light, very dificrent from the 

 fudden flafli called lightning. 



Vol. f.— Sr.i'TEMLEK 1797, M «q [ w^ 



