Proceedings of the Polytechnic Association. 1023 



iron should be corroded. The piece was one and a half inches square 



and five inches long. The oxydized portion was ninety -two per cent 



zinc. The curved sliape this piece of zinc is common to all cases 



of oxydation. 



Patent Laws. 



Mr. Thomas D. Stetson spoke at length on tlie patent laws of dif- 

 ferent countries. The United States patents are the most neatly 

 executed. We have the finest patent office in the world. It is built 

 ' in the form of a hollow square, and covers two blocks. It has some 

 50,000 models, a great number of drawings, &c. About 200 patents 

 are issued every week. The Patent office, as now managed, is a 

 source of pride to every American. The English Patent office requires 

 no models, and makes no examinations. With us, novelty, utility 

 and improvement are the essentials that make a good patent. The 

 English patents are elaborately made out on parchment, with a num- 

 ber of verbose legal formulas ; with a waxen seal some five inches in 

 diameter and one inch thick (Mr. Stetson here exhibited the seal). 

 An English patent costs some eleven dollars, but the patent fee is 

 now payable in installments. In France a patent can be had for a 

 government fee, which has to be paid yearly. The American govern- 

 ment patent costs only thirty-five dollars for seventeen years. Here 

 it is very easy to procure a patent. Within a few years the regula- 

 tions have been radically improved. A patent can be got through 

 with all that is required in about twenty-five minutes. The system 

 of examinations pursued here cause many bad patents to be rejected. 

 We make one general round charge, and that covers all expenses. A 

 Spanish patent will cost some ^200, They are engrossed on single 

 sheets of common foolscap paper, and merely stamped in the place 



of seals. 



Aetificial Illumination. 



Dr. Vanderweyde briefly explained the theory and practice, lighting 

 by means of the calcium light and the Argand burner. With this 

 burner, he said, the more air admitted to it, the less gas is consumed ; 

 but, if too much air, the flame will become blue. The gi-eatest lumi- 

 nosity at the smoking point ; when the smoking just stops, the light 

 is at its maximum. Zirconia, lime and magnesia are the three sub- 

 stances which are used in the hydro-oxygen apparatus for an intense 

 light. The magnesium light is produced b}^ simply burning that 

 metal. Strips of magnesium metal are now used by photographers 

 to take pictures in the evening. The doctor illustrated his 



