Obituary

Mr. John Trumbull Marshall, assistant engineer of the Edison Lamp Works at Harrison, N. J., died in Bermuda on January 1, 1910, at the age of 50 years. Mr. Marshall was born in Kingston, N. Y., and was graduated from the scientific department of Rutgers College in 1881. In October of the same year he entered the employ of the Edison Lamp Works. His first work was in connection with photometry and testing of lamps. In 1883 or 1884 he invented a comparison method of photometering lamps. By this method the voltage of a lamp at nominal candle-power is determined without the use of any electrical instrument by placing it in series with a lamp of known candle-power and voltage and observing their relative intensities. During the last few months Mr. Marshall completed and put in successful operation an improved method of comparison of lamp measurement known as the watts-per-candle photometer. Besides specializing in photometry, Mr. Marshall gave much attention to the manufacture of carbon filaments, especially methods of carbonization and of metallizing filaments in use at the present time. He became an Associate of the Institute on October 1, 1889, and on November 12, 1889 was transferred to the grade of Member.