Geological Society. 153 



has attained its greatest exuberance, namely, when the summer 

 months are past and the light is beginning to decrease in its in- 

 tensity and the days to shorten. So exactly, indeed, are the ener- 

 gies of the plants regulated by the amount of light to which they 

 are exposed, that a constant arrangement, such as that here des- 

 cribed, affords an excellent indication of the variation of the seasons 

 in different years, or might even be made a rough measure of the 

 total amount of light from month to month. 



But while the demand for carbonic acid on the part of the plant 

 varies in this manner with the seasons, the amount of that gas pro- 

 duced by the respiration of the fish is very nearly the same all 

 through the year. Whence, then, does the plant obtain that addi- 

 tional quantity of food which its stimulated energies require during 

 the spring and early summer months, and which its rapid and 

 luxurious growth show to be readily supplied ? After what has 

 been stated, I think the source must be apparent to every one : it 

 is the carbonic acid which has been gradually accumulated, and 

 rendered innocuous to animal life from its being held in combination 

 with carbonate of lime, in so marvellous a manner during the 

 winter months. Stored up, yet held in feeble combination, a com- 

 bination so weak that the vital forces of the fresh-growing vegetation 

 can easily overcome it, and resolve once more into carbonate of lime, 

 carbon, and oxygen the bicarbonate of lime contained in the water *. 



Thus beautifully are the necessary irregularities in the purifying 

 action of the plant compensated and provided for, that the balance 

 of existence between the animal and vegetable organisms be not 

 disturbed or overthrown, and thus additional proof is furnished, if 

 such were needed, of the wisdom of that creative power that has 

 ordered all things to work together for good, and by endowing certain 

 bodies with such seemingly minute and insignificant affinities, main- 

 tains the glorious harmony of the whole. 



GEOLOGICAL SOCIETY. 

 [Continued from vol. xxxiv. p. 549.] 

 January 8, 1868.— Warington W. Smyth, M.A., F.R.S., 

 President, in the Chair. 

 The following communications were read : — 

 1. " Notes on the Lower Lias of Bristol." By W. W. Stoddart, 

 Esq., F.G.S. 



Three sections in the suburbs of Bristol were described by the 

 author as exhibiting the following strata in descending order, 

 namely:— at Ashley Down, (1) Ammonites-costatus bed, (2) Saurian 

 bed, (3) Ammonites-Conybeari bed (commencement of the zone of 

 A. Bucklandi), and (4) Lima-beds; the succeeding beds are covered 

 up for a short distance, and then, in Montpelier quarry, are exposed 

 (5) Ammonites-torus bed, (6) Echinoderm-beds, (7) Ammonites- 



* The rapid growth of submerged vegetation in rivers and waters containing 

 a considerable amount of carbonate of lime must have been observed by all 

 interested in the subject, in some cases obliging the cleansing of such streams 

 three or four times during the year. 



