General Notices. 97 



accounted for on the principle of gravitation. It is to be observed, that the 

 gravitation takes place in consequence of the softening of the soil by rains, 

 when the lighter particles being softened, the adjoining heavy ones over them 

 naturally take their place. Every one must have observed that a brick or a 

 stone, laid on the surface of the ground, no matter how firm that ground may 

 be, gradually sinks into it. We have only to refer to the name bricks in 

 Messrs. Loddiges's arboretum. It would be easy to prove the whole of this 

 theory, by filling two flower-pots with soil, and laying a stratum of dung at 

 the bottom of the one pot, and a coating of lime on the surface of the earth 

 in the other. Both pots should then be plunged into the ground in an open 

 situation, where they will be exposed to the rain ; or the experiment may be 

 accelerated by watering the pots every day with a fine-rosed watering-pot. — 

 Coud. 



Effect of Carbonic Acid on Vegetation. — M. Traviranus, in his Physiologic 

 Vegctale, has stated that vegetation is not so active near springs where carbonic 

 acid is disengaged. • In replj' to this assertion, M. Schleiden has inserted, in 

 Wiegmann's Journal of Natural Histori/, a note to prove the contrary. Ac- 

 cording to M. Schleiden, the numerous springs in the valley of Goettingen 

 contain a great quantity of disengaged carbonic acid gas, and some carbonate 

 of lime in solution; and the vegetation of their waters and on their sides is 

 always very vigorous, n)ore advanced in spring and prolonged in autumn, than 

 in other situations. Amongst the plants growing in the water was Smxn an- 

 gustifolium ; and among those growing on the sides of the springs were i?anun- 

 culus lanuginosus, the pilewort, the marsh marigold, and Primula eliitior. It 

 appears from this, that carbonic acid, either when disengaged, or when absorbed 

 by water, exerts a beneficial influence on vegetation. (^U E'cho du Mo)ide 

 Savant, Nov. 4. 1837.) 



Phosphorescent Plants. — M. De St. Hilaire says that the agaricus (I'olivier) 

 gives out a yellowish phosphorescent light in the dark ; and it is supposed by 

 M. Vallot that the notices of phosphorescent plants in ancient writers refer to 

 that of the agaricus. There are, however, flowering plants which also emit 

 phosphorescent light; such as the -Euphorbia phosphorea L., the milky juice 

 of which possesses this quahty. (Ibid.) 



Loss of Species of Plants. — M. DeSt. Hilaire states that many species of plants 

 have been lost within the period of history. Within a few years, many species, 

 quite common in the environs of Paris have become very rare ; SdWa italica, 

 (S'partium purgans, and Pseonia corallina have entirely disappeared from the 

 neighbourhood of Orleans ; and, even in our own days, the rocks of Vaucluse 

 have been completely despoiled of the Jsplenium Petrarchc?. Is it not pos- 

 sible, then, he adds, that many flowering plants, really phosphorescent, may 

 have been lost in the long period which has elapsCLl since the dajs of Demo- 

 critus, Pliny, and Josephus ? (Ibid.) 



SilAworins fed upon Bice. — In a Chinese work on the culture of the silk- 

 worm, lately translated into French by M. S. Julien, a curious process is 

 mentioned, the correctness of which has been proved by experiment. It is 

 said that, in China, in order to supply more nourishment to the silkworms, the 

 mulberry leaves upon which they feed are powdered with the flour of rice. 

 But M. Bonafons of Turin, who translated the work into Italian from the 

 French, wishing to prove the truth of the Chinese process, powdered the mul- 

 berry leaves with the flour of rice, with wheat flour, and with other fecula ; 

 and found that these various substances, which otherwise are not eaten by the 

 silkworms, become, in this case, excellent nourishment, and cause the worms 

 to dcvelope themselves rapidly. The cocoons of the silkworms fed upon rice 

 flour are much finer and heavier than usual. The other kinds of fecula did 

 not produce a satisfactory result ; but it is to be hoped that, by experiments 

 made among the European keepers of silkworms with different farinaceous 

 substances some substitute may be found for the rice. (Ibid.) 



Preservation of Vegetables, — M. D'Eaubonne prepared a case in such a 

 manner as entirely to exclude the air; he then mixed potter's clay and cow's 



Vol. XIV.— No. 95. ii 



