Watertown Republican

The Phonograph in Engineering.

From the Pittsburg Dispatch.

The question whether the practical everyday utility of the phonograph is likely to prove, after all, of much importance has been very freely discussed and the result is a decided difference of opinion. There is no doubt, however, that one of its latest applications, though it may be confined to a somewhat restricted field, is of great importance to the engineering world. It is admitted that the life of an iron or steel bridge cannot be definitely prolonged, and yet engineers do not possess any completely satisfactory method of determining the actual condition of these structures, on the strength of which so much depends. So long as no actual deformation has taken place, the iron may here or there be assuming a crystalline condition, or may be seriously oxidized underneath the coating of paint, and yet the extent of the evil can easily remain undiscovered. It is now proposed to employ the phonograph in connection with a microphone and telephone to register the nature of the vibrations of the bridge as a whole or in sections under a rolling load and to preserve the record for comparison with subsequent tests carried on at regular intervals. The direct comparison of two phonographic records cannot be carried out with sufficient accuracy and an optical method is therefore employed, and a beam of light is reflected from the vibrating plate after the manner of the well-known Lissajous figures. It would, of course, be necessary to secure a long series of such records before the results would be capable of complete interpretation but there seems good reason to believe that by this means reliable indications of a change in the molecular structure of the material can be obtained.