rake it together, let it drain, and refine it by their own dry method.

This dry method of refining table salt is based on the following conditions:

(1) We have a mixture of anhydrous sodium chloride and two hydrated magnesium salts, to wit: magnesium sulphate and magnesium chloride; sometimes also calcium chloride and sulphate of sodium is present.

(2) If these two magnesium salts are removed, it is selfevident that the residue will be pure table salt (NaCl).

(3) If this mixture of salts be heated and all the water of crystallization contained therein be driven off, the magnesium salts are converted to a fine, pulverulent condition which may be removed by a current of air. Experiments have fully proven the correctness of this method. I am sorry to say that the name of the inventor of the process has not been disclosed. However, from data obtained in California and in Salt Lake City, Utah, I am satisfied that the Mormons exploited the first plant for refining table salt on a large scale by the dry process.

The refining process carried on at the work near SaltAir, Utah, is a continuous one. A slowly rotating cylinder, apparently made of wood, about 30 feet long and roughly estimated about 6 feet in diameter, is caused to make about one revolution in four or five minutes. In the inner part of this cylinder is fixed an iron cylinder about 12 or 16 inches in diameter, which is charged, as I am informed, with superheated steam, supplied and connected by the necessary coil and steam generator. This is the dryer.

The salt, in the wet state, is fed into the hottest end of the dryer by a screw carrier, made of iron. Within this long cylindrical dryer it is slowly moved forward towards the other end by means of an arrangement that keeps the layer of salt evenly and thinly spread over the whole length of the dryer. The water is thus vaporized and carried off through a flue urged with the aid of an exhaust fan driven at considerable speed. The exhaust fan which carries off the vapor of water at the same time carries with it the now fine dust of the two magnesium salts; thus doing double service.

At the further end of the cylinder the dry hot salt falls upon a sieve, where another separation takes place, namely: all of the material that has formed into lumps is caught upon the sieve. On taking a sample of the sifted salt from the receiving box the salt felt quite hot. Looking critically upon the small crystals I saw that there was still some little of the white dry powder adhering to them, indicating that the magnesia salts had not been entirely removed. I made the remark to the guide (one of the workmen) who showed me through the works, that the separation was not complete; and he acknowledged the fact that by one blowing as he termed it-the separation of the impurities could not be completely effected, but that a second and third grinding and sifting and blowing was required to finish the salt for table use.

The successive transportations of the material were effected as in a flour-mill, by horizontal and vertical belts on which triangular boxes were fixed to receive and carry the salt to another point. To avoid any contamination, through dust or dirt, the entire system of belt carriers was run in quadrangular wooden boxes well fitted together.

The best grade of salt, for table use, is ground very fine; and it is not possible to recognize the presence of any of the magnesium salts without a chemical analysis. I did not take along a sample for chemical examination, and hence withhold judgment with regard to the perfect separation of the magnesium salts from the sodium chloride for table use produced at the Works of Salt Air. So far as appearances go the article was good and had no bitter taste. Whether the salt will keep dry in a moist atmosphere is a question I am unable to answer. I saw some samples of salt from the Pacific Coast at the St. Louis Exposition which showed signs of moisture to some extent. While there I tried to find samples of salt from Salt Air, Utah, but without success. My object was, of course, to observe what effect, if any, the moist atmosphere of St. Louis would have upon the product.

I could hardly believe it possible that all the magnesium salts could be removed from chloride sodium by the dry VOL. CLIX. No. 949.

4

process; but it seems that the article is at least as good as the French, and that suffices. At any rate, the material is produced in the West on a very large scale, considering the population.

The output is from 150,000 to 200,000 tons annually, which is far in excess of what is needed for home consumption. It is even exported to the Hawaiian Islands and other points. It is accepted by the consumer as satisfactory, and that proves better than any other criticism that the dry process of refining table salt is an accomplished fact.

The current of forced air which drives the dry, dusty magnesium salts away from the sodium chloride along with the vapor of water carries with it some of the sodium chloride. This is shown by the fact that on top of the building, near the flues, there is a fairly thick, white deposit of the mixed salts, which would run down the roof if much moisture were in the air.

In the Salt Air Works this separated mixture of salts is not thrown away, but is made available by mixing it with about one-fifth its weight of sulphur and heating the mass to form blocks. These keep fairly dry and are sold to the dairymen and cattle raisers as lick-salt. It finds a market, and my informant told me that the demand for it was greater than the supply.

SUBMERGED COAL EXPERIMENTS.

Some time ago we drew attention to the experiments that were being carried out by the British Admiralty with submerged coal. In May, 1903, five crates of coal, each holding two tons, were sunk in a basin at Portsmouth, and a similar quantity was placed at the coaling point on land, in small heaps, covered with tarpaulins. Six months ago some of the submerged coal was raised and burnt, in conjunction with a similar quantity of that which had been kept on land, and the results showed that the submerged coal had greater calorific qualities. Owing to the success of this test, further experiments are to be carried out on the same basis.-Scientific American.

STEEL RAILWAY TIES.

Officials of the Lake Shore Railroad have placed an order for 7,000 steel ties to be used as an experiment, probably near the eastern terminus of the road at Buffalo. Part of the order will be used on the New York Central, and if the results are satisfactory it is expected that a more general use of steel ties will be made by the Vanderbilt roads.

Mechanical and Engineering Section.

(Stated Meeting held November 25, 1904.)

The United States Patent Laws: Historically and Practically Considered.*

BY CYRUS N. ANDERSON,
of the Philadelphia Bar.

Several years ago a writer in the Iron Industry Gazette, an English publication, said: “Disparagement of patents is common and easy, but it should not be forgotten by those who sneer at inventions that, out of a total of eight billions of capital invested in manufacturing in the United States, patents form the basis for an investment of about six billions. Evidently, the United States system of encouraging invention that has resulted in the patenting of over 500,000 inventions is a system which is exceedingly wise and valuable. The only thing that has enabled manufacturers to make so wonderful a progress in the United States is its patent system.”

Up to the present time, there have been granted in the United States nearly 800,000 patents, and, while I have no recent figures, there is no doubt but that the proportion of capital invested in manufactures with patents as a basis is as great, if not greater, now than it was when the foregoing statement was made.

At a time when the right of property in patents, or rather in patented inventions, is so well recognized, it strikes one as a curious fact that there ever was or should have been a time when a right to such property was not recognized. Yet the fact is that in comparatively recent periods, considered in the light of the world's history, property rights in connection with inventions were not recognized, and if a man was possessed of an inventive turn of mind and was an

* Read at the stated meeting of the Business and Professional Club for November, 1904, and (by title) before the Mechanical and Engineering Section of the Institute, November 25, 1904.

inventive genius, and made inventions or improvements in machines or in mechanical devices or in the art of doing things, he had to stand by and see others enjoy equally with him the benefits of his intellectual thought and effort.

In the very earliest history, the right of property in tangible things was recognized, but an exclusive right in intellectual property, such as inventions and writings, was not regarded as a natural right, and the right to such property was only established as a result of advancing and improved civilization.

It seems that quite early in England the practice grew up under which the Crown, as a matter of grace and favor, but not of right, granted to the inventor of a new manufacture or a new art, the exclusive right for limited periods to his invention or improvement, and it is reported that in the fourteenth century, in the reign of Edward III, some wise subjects of the realm, alchemists they were, invented or discovered a philosopher's stone. A commission was appointed by the King, consisting of two aldermen and two friars, who, after an investigation, which, of course, was very carefully made, reported that the philosopher's stone possessed merit, and upon this report the King granted an exclusive right to the discoverers to manufacture and sell the philosopher's stone.

When the nature of intellectual property is considered, it seems somewhat anomalous that rights of property therein should not have been recognized from the very earliest times.

Professor Shaler has said: "When we come to weigh the rights of the several sorts of property which can be held by men, and in this judgment take only the absolute questions of justice, leaving out the limitations of expedience and prejudice, it will be seen clearly that intellectual property is after all, the only possession in the world. The man who brings out of nothingness some child of his thoughts has rights therein which cannot belong to any source of property."

Mr. Fessenden, in his work on patents, published in 1821, says: "In a moral as well as in a political point of view,