CHAPTEK XLIII.

The Tesla Mechanical and Electrical Oscillators.

On the evening of Friday, August 25, 1893, Mr. Tesla de-livered a lecture on his mechanical and electrical oscillators, lie-fore the members of the Electrical Congress, in the hall adjoin-ing the Agricultural Building, at the "World’s Fair, Chicago. Be-sides the apparatus in the room, he employed an air compressor,which was driven by an electric motor.

Mr. Tesla was introduced by Dr. Elisha Gray, and began bystating that the problem he had set out to solve was to construct,first, a mechanism which would produce oscillations of a per-fectly constant period independent of the pressure of steam orair applied, within the widest limits, and also independent offrictional losses and load. Secondly, to produce electric cur-rents of a perfectly constant period independently of the work-ing conditions, and to produce these currents with mechanismwhich should be reliable and positive in its action without resort-ing to spark gaps and breaks. This he successfully accomplishedin his apparatus, and with this apparatus, now, scientific men willbe provided with the necessaries for carrying on investigationswith alternating currents with great precision. These two in-ventions Mr. Tesla called, quite appropriately, a mechanical andan electrical oscillator, respectively.

The former is substantially constructed in the following way.There is a piston in a cylinder made to reciprocate automaticallyby proper dispositions of parts, similar to a reciprocating tool.Mr. Tesla pointed out that he had done a great deal of work inperfecting his apparatus so that it would work efficiently at suchhigh frequency of reciprocation as he contemplated, but he did notdwell on the many difficulties encountered. He exhibited, how-ever, the pieces of a steel arbor which had been actually tornapart while vibrating against a minute air cushion.

With the piston above referred to there is associated in one ofhis models in an independent chamber an air spring, or dash pot,