62 . b REPORT— 1849, 
quantity present might be estimated at 13 per cent. as compared to the 
volume of water, all the fish experimented upon speedily perished. 
Nor was this merely the case with freshwater species, for I have had an 
opportunity within the last fortnight of repeating the same experiments at 
Ryde on certain sea-fish obtained off that coast. The species operated upon 
were those called Golden Maid (Labrus), two sorts of Pipe-fish (Syngnathus), 
Rock-fish ( Gobius niger), Bull-fish ( Cottus secorpius), and Flounder (Platessa 
flesus). Of these the Pipe-fishes and the Flounder remained alive for many 
hours in a tub of salt water containing 5 per cent. of carbonic acid, nor did 
they appear to suffer in consequence. When the amount was equal to 10 per 
cent., the Golden Maid (Labrus) was almost instantly affected, as were also 
the Pipe-fishes above operated upon. 
Although therefore the difficulty of keeping sea-fish long alive in small 
quantities of salt-water, after they have been removed from their natural 
element, renders it more difficult to arrive at satisfactory results with them 
than with freshwater species, I think myself upon the whole warranted in 
concluding, that both kinds are equally tolerant of the smaller amount of car- 
bonic acid, and alike susceptible of the poisonous influence of the larger. 
Supposing however no error to exist in the calculation I have made above 
as to the amount of carbonic acid present in the water to which the minnows 
had been subjected, it will follow that whilst 5 per cent. is innoxious to some 
fish, 3 per cent. is noxious to others, and that the power of resisting its dele- 
terious influence differs in different species. Nevertheless there seems reason 
for supposing, that an amount of carbonic acid in the atmosphere considerably 
larger than that which exists at present, would not communicate to the waters 
of the sea and rivers properties incompatible with the life of many fish. 
Although reptiles are not supposed to have existed generally at so early a 
period as that of the carboniferous formation, yet as saurians have been de- 
tected in the coal-beds of Greensburg in Pennsylvania, and in those of Saar- 
bruck near Treves*, which are regarded as belonging to the same epoch, and 
as they made their appearance so abundantly in that which comes next to it in 
point of antiquity, it appeared worth while to ascertain what power of resisting 
the influence of carbonic acid might be possessed by the tribes now in being 
which belong to the same class of animals. 
_ With reference however to this department of the inquiry, the experiments 
hitherto made by myself are far from numerous: I have kowever found, that 
frogs introduced under a bell-glass containing 5 per cent. of carbonic acid 
gas, appeared not to suffer, although they were killed when its proportion 
amounted to 10 per cent. Similar results were also obtained in experimenting 
upon newts; so that it would seem, as if, in accommodation to those arrange- 
ments of nature which were calculated to impart a greater luxuriance to the 
vegetation of the period alluded to, and to bring about during its continuance 
a larger accumulation of carboniferous matter, the lower tribes of animals, 
which at that time alone occupied the earth, were rendered less susceptible of 
the injurious influence of carbonic acid, than the higher orders subsequently 
created are found to be. 
In conclusion then I may remark, that the general tenor of these experiments, 
so far as they have as yet gone, justifies us in inferring, that there is nothing 
in the organization of those plants and those animals of the present day, which 
appear most nearly allied to such as were in existence during the carbonife- 
* See Lyell’s Travels in America, 2nd Series. 

