themselves; in which case, in addition to the profit on his regulator, he gets the normal business profit on manufacture of the whole machine. Sometimes a patent can be divided into separate rights. If so, the patentee can probably get nearly as much from the purchaser of each single right as that purchaser would pay him for all the rights put together. The Goodyear rubber patent was thus divided, the owner licensing one concern to make rubber shoes, another clothing, another tubing, another combs, etc. Again, it is important whether much or little capital is needed, and whether there is a continuing expense. A telephone system has to be constantly supervised by experts, while an artificial sidewalk can be sold once for all. The latter, being essentially a local business, can wisely be divided into territorial rights or licenses; the telephone can also be divided, or can be worked as a unit.

The patent may be sold for a lump sum or a royalty. On the principle that a bird in the hand is worth two in the bush, an inventor will sometimes get more by selling his invention for a lump sum at the start. As a rule, however, the main profit from a patent is derived by the person who holds and exploits it year after year. In return for this greater chance of gain, this person has to stand the risk of loss in case a substitute and non-infringing device is subsequently invented; and he has to bear the financial burden and risks of carrying on the business. The article, possibly, may be of short-lived vogue, like "Pigs in Clover," though immensely profitable while it lasts; or the patent may be proved to be invalid.

Sometimes a patentee can sell separate territorial rights in each state or county. There are nearly 3,000 counties in the United States. Suppose county rights were sold at $10 each, with provision for a small royalty on sales. The inventor would net a comfortable sum whether any sales of the articles were subsequently made or not.

The patent can be worked on a royalty basis with very little capital. The patentee must have enough to take the necessary steps towards placing the patent and looking after it. In fixing the roy

alty, the cost of collecting the same and of a proper supervision over the extent of the licensee's use should be remembered; and every royalty contract which grants an exclusive right should contain a clause guaranteeing an annual minimum payment, lest the licensee, having got possession of the patent, should put it away unused and no royalty accrue.

Specimen Problems

Let us consider three different kinds of inventions:

First. Some article of general use— say a shipping tag. This can be made and sold by the inventor himself, if he wishes. The article is salable to numerous consumers all over the country, and can be supplied from a central factory. The total probable sales can be estimated, and from them the total profit; thus a valuation for the patent can be arrived at with a fair degree of accuracy. If the patentee wishes to work it himself, but lacks capital, he can sell some territorial rights, and thus raise capital to work the remaining territory himself. If an offer of a lump sum is made for the patent, he can judge whether it is adequate. If inadequate, he can afford to wait, even though he does only a small business in the meantime; the patent will be more salable rather than less as time goes on and as the invention becomes better known.

Second.-Suppose the invention to be one of the new kinds of rapid-cutting tool steels. Such a patent may be worked by making and selling tools, or by selling the patented steel to makers of tools, or by licensing one or more concerns to make the steel itself. Inventions of this character are so new that the scope of the market for them and the real value of the invention cannot be accurately judged at the present day. All that is known about the future of such steels is that the demand for them will ultimately be enormous. Which particular kind will live in the fight, and how low profits will be cut, it is too early to estimate. Hence, if a man sells such a patent for a lump sum, he must sell it at what may prove to be a sacrifice. If he delays, or if he sells on a royalty basis, he may get a larger sum; but he takes the chance of seeing his possible profits

will recognize this illustration as a reproduction of a card which they also received, except that each found his own name, date, and number in the place here occupied by another. The wording of the card will fit any sort of device. Of course, the recipient is not aware that the same flattering statement is mailed to a large number of other patentees each week. Does anyone believe that this "agent" has actually "had an inquiry" for the devices of all of them?

As a matter of fact, this particular patent relates to an improvement in the mail-boxes used by the Government for collection of letters at street corners, etc. To say that the sender of the postal card has "had an inquiry for a device like yours" and "can dispose of it for you, either in state rights, royalty, or outright," is absurd. Undoubtedly this improvement will be of great benefit to the public in each State, if the Government adopts it; but it is not the sort of thing for which "state rights" can be sold.

Subsequent correspondence showed that the "agent" was anxious to receive a preliminary registration fee of ten dollars, upon receipt of which he would try to sell the patent; and would ask no pay for his services unless a sale were effected. So far as the author of this paper knows, that would be done sincerely; but there is a suspicion that a comfortable living can be made from registration fees alone, even if the efforts to sell are unsuccessful.

For instance: Suppose that only ten patentees each week out of the weekly crop of five hundred, more or less, are induced to send the "agent" ten dollars each. Figure it out.

This is mentioned merely as a type of the offers a patentee receives. Other "agents" desire to procure Canadian and foreign patents for the inventor, always at bargain prices, and usually accompanied by testimonials having a strong savor of quack medicine advertisements. The patentee ought to remember the advice previously given:

Services really worth having, cost

money.

Men who are really competent do not need to cut rates.

A matter worth doing at all is worth doing right.

"Working" the Inventor

The confident inventor is sometimes "worked" as follows:

A firm of "bankers and brokers," with an impressive letter-head, write that they are in the business of promoting and financing new inventions, and would like to take hold of Mr. X's patent, as it looks profitable. They suggest forming a corporation, say of $100,000 capital stock, giving the majority of the stock to the patentee. The broker will do all the business of incorporating, and will not ask for any fee until the company is successfully under way, but will then receive a commission on whatever stock he succeeds in selling. This idea is so plausible that the victim assents. Then the broker explains that in order to make the scheme. a success it is necessary for some big Trust Company to act as trustee. The broker will arrange all that; but $500 will be necessary to pay the Trust Company for its services, and to pay for preparing the papers, opinion of the Trust Company's counsel, etc., etc. This also is plausible; the client advances the money; and a corporation is formed. After long delay, the client becomes impatient, and is finally informed by the broker that it has proven impossible to sell any stock, because no investors were satisfied with the proposition. Result:client $500 out; broker $300 in. Sometimes the Trust Company "wrinkle" is left out, but the effect is the same.

The moral is-Deal only with thoroughly trustworthy people. Don't be misled by appearances. This does not mean that no agent or broker may be employed, or no corporation formed. Salesmanship and the art of negotiating are specialties just as much as the art of stone-cutting or of oratory; and frequently the formation of a corporation is the very best way to finance a patent. -Only, don't be gullible. Inventors and men of genius are proverbially poor busi

ness men.

How to Sell

One method of selling a patent or getting capital is as follows:

First. Find a man with sufficient money. Advertise, if necessary. A man who is familiar with the particular business to which the invention relates will

most easily appreciate the true value of the patent.

Second. Make him understand the invention and see the value in it. A clear drawing helps in this, with a simple printed description. These should be neat, accurate, and clear. In addition, and far more convincing, is a working specimen, or what is sometimes called a "working model."

Third. Most convincing of all is the record of actual manufacture and sales showing clearly what it costs to build the thing, how it can be sold, and how well it appeals to the public. No argument is so conclusive as the fact of profits actually made. Therefore, get a business started; capital will then come in and spread the business over the country. Atwood, the inventor of the sun burner and straight chimney, having failed to induce manufacturers to place his improvements on the market, borrowed the money to have his patented articles made, and then himself peddled the same from an open wagon around the streets of Chelsea, Massachusetts. In eight years thereafter, he had accumulated seven or eight hundred thousand dollars out of his invention.

Fourth. A man who is by temperament or experience a salesman or solicitor can sell goods and get capital where another man would fail. The assistance of such a man is valuable.

Fifth. If you have a good article and your efforts are unsuccessful at first, don't give up. Be diligent. Keep everlastingly at it.

When a sale or agreement is about to be consummated, a lawyer should invariably be consulted to prepare the papers a lawyer having experience in dealing with patent rights. The dangers are too great to justify unskilled persons in preparing the papers themselves. Special warning must be given against the use of the form of assignment of an undivided interest in Letters Patent, contained in the appendix to the "Rules of Practice" published by the Patent Office. That form is, no doubt, sufficient for its purposes, and a pitifully large number of the patents issued each week are assigned in that way. The objection is that this form of assignment results in each person, assignor and assignee, having

the right to use the invention as freely as if he owned the whole of it, and to license others to use it, but with no check on competition between the owners, and neither having any right to share in the profits made by the other. A better way is to have a title stand in the name of a single person-a trustee, if need be; and to have the intended rights and duties of the respective parties clearly defined in the instrument.

From the Buyer's Standpoint

All patents issued are presumed to be valid; but the Government does not guarantee their validity, and a seller of a patent cannot wisely give such a guarantee. The official search may have overlooked some anticipating patent. Frequently the prior art contains somewhat similar devices which the Examiner did not have occasion to mention, but which materially affect the scope of the patent in question. Consequently every buyer of a patent should have an exhaustive search of the records made, and an expert opinion as to the scope and validity of the patent. If he and all the public are free to make some device equally good, which is disclosed by the search and is not covered by the patent, he is foolish to pay money for the patent. Every intending competitor ordinarily makes a similar search in order to find, if possible, a lawful competing method. The buyer should also have a search of the title records made, just as in the case of real estate.

If an invention proves commercially successful, a host of infringers spring up-people who seek either honestly or dishonestly to obtain for themselves some of the fruits of the invention. The patentee, on proving his case, may get a writ of injunction from a Circuit Court of the United States, restraining any such person from infringement, and awarding to the patentee the damages he has suffered. and the profits which the infringer has made. If the infringer continues, the Court will fine or imprison him as for contempt of court. The getting of an injunction consumes a number of months. and sometimes years; but when the validity of a patent has once been established, the Court will grant injunction promptly, and the patentee remains in command of the field during the remaining life of the patent.

T

HE various practical applications of compressed air cover a range of pressure from a fraction of an ounce to several thousand pounds per square inch. To produce the required supply of air with proper pressure and economy, numerous types of compressors, each having its peculiar and appropriate field, have been designed. These are, in the order of the pressure pro

duced: the disc fan, the centrifugal blower, the positive blower, the blowing engine, the direct-acting compressor, and the compressor with crank and flywheel. By the operation of all these, the same result is produced-the delivery of a quantity of air under an increased pressure and correspondingly increased temperature, and the subsequent rapid loss by the air of its excess of temperature, with a proportionate decrease in volume. Most of the problems in the design of compressors are created by the heating of the air during compression and by the effects so produced upon the apparatus.

The Disc Fan

The disc fan, corresponding to the marine screw propeller in action, is useful for producing a flow of air of considerable volume but with almost inappreciable increase of pressure. It is thus suitable for purposes of ventilation in expelling foul air, gases, or smoke, or for removing dust, fine shavings, and waste particles from woodworking and grinding machines. The power expended in revolving the fan goes in great part towards whirling the air current around in the fan casing and pipe-a waste of effort which limits the application of this