As far as chemical composition is concerned, marble and whiting are analogous; both are carbonates of lime, and when equally pure both contain about the same amount of carbonic acid. Whiting, however, is rarely, if ever, as pure as marble. It consists chiefly of the remains of extremely small animalcules, containing, according to Bechamp, more than two millions of these in 100 grammes. M. Bechamp even went so far as to state, in a communication to the French Academy of Sciences, that, besides these remains of organized beings, chalk contains innumerable living organisms, smaller than any hitherto known. This fact, however, has been disputed, and it has been held that the living animalcules observed by Bechamp were not present in the chalk when first taken from the quarry, but were subsequently absorbed when the chalk was brought in contact with the atmosphere. Be this as it may, the fact none the less remains that whiting, when it reaches the generator, contains a considerable amount of organic matter. Although interesting in itself, it is of no consequence, as far as the present discussion is concerned, how the presence of this organic matter is to be accounted for; there it is, and, when the consumer complains of the unpleasant smell or of the fishy taste of the "soda "water, it does not require much perspicacity to see that some of the gases from the decomposed organic matter have followed the carbonic acid gas through the gas-washer and into the beverage.

The crystalline structure of marble indicates that at some period the chalk from which it is probably derived was in a state of fusion under great pressure, and consequently it cannot possibly have contained any organic matter. It is known that the carbonates may be melted under pressure without parting with their carbonic acids. On cooling, the melted mass of carbonate crystallized and assumed the compact form in which the marble is found to-day, so unlike the friable, spongy structure of whiting, which renders the latter exceedingly liable to absorb impurities, while marble is practically non-absorbent.

Another point in favor of marble dust as against whiting, for use in carbonating beverages, is the fact that the gas is evolved much faster from the latter than from the former, causing a violent ebullition and increasing the liability of priming, that is to say, of acid and marble being carried over into the gas-washer. It is a natural mistake to suppose that because from whiting the gas is evolved faster than from marble, it follows that more gas is obtained in the former case than in the latter. This is by no means true, for in the case of the marble the gas is slowly but steadily emitted to the end of the process, while with whiting the ebullition, though more violent, is sooner over.

There is still another point in favor of marble dust. In the course of some recent experiments which were made with marble and whiting, it was found that the latter required to be mixed with about twice as much water as the former, in order to obtain the best results from the thorough mixing of the acid and carbonate. This fact implies the necessity of using a larger generator, or of charging the apparatus oftener, to produce a given amount of gas with whiting, than to evolve the same amount with marble; which means, in either case, an additional expense.

Another important fact in favor of marble dust is, in this country, that it is cheaper than whiting. Until recently no chalk beds were known to exist in this country; but in his geological survey of Dakota, Prof. F. V. Hayden discovered beds four hundred miles in extent along the Mississippi River. Should large deposits of this mineral be found in the United States, it is probable that the price of whiting would drop to some extent; but we think we have conclusively shown that in no case would it become the equal of marble dust for use in manufacturing carbonated beverages.

In countries where there is an abundance of whiting, and where it can be had in a purified state cheaper than marble dust, it is and may be exclusively employed, care being taken to purify the liberated gases.