HENRY AUGUSTUS ROWLAND 415 



certain that the work could not have been done better if it had 

 been done in a palatial laboratory. The remark made by Garfield 

 that " Mark Hopkins at one end of a log was a good enough college 

 for him" might be appropriately modified to suit this case, " Row- 

 land in a back kitchen is a good enough physical laboratory for 

 the highest type of work." 



The research on the Mechanical Equivalent of Heat was pub- 

 lished in full by the American Academy of Arts and Sciences, the 

 expense of publication being met by a fund established by Rum- 

 ford, and in this connection it may be noted that this same Ameri- 

 can Academy awarded the Rumford prize to Rowland. Later, 

 in 1 88 1, the article describing his results was crowned as a prize 

 essay by the Venetian Institute. 



In 1 88 1 Rowland was appointed a delegate of the United States 

 to the International Electrical Congress that met at Paris. Realiz- 

 ing the importance of the accurate measurement of electrical 

 quantities he made a thorough study of the fundamental quantity, 

 the ohm. This work was afterward repeated and extended at the 

 request of the United States Government. The results are of 

 great important and are generally accepted. 



Perhaps the best known achievement of Rowland is the concave 

 grating. In order to study light from different sources it is neces- 

 sary to analyze it. This is most readily accomplished by means 

 of a prism. As is well known when sunlight is allowed to pass 

 through a prism it emerges in the form of a spectrum. The 

 white light of the sun is thus shown to be made up of lights of 

 different colors the well-known colors of the solar spectrum. 

 Now every light has its own characteristic spectrum, and by 

 observing the spectrum much can be learned in regard to the 

 nature of the source of the light. By such observations, for ex- 

 ample, it is possible to tell what chemical elements occur in the 

 atmosphere of the sun and of the fixed stars. Light can be ana- 

 lyzed also by allowing it to fall upon a surface upon which a large 

 number of parallel lines have been ruled very close together. Such 

 plates are called diffraction gratings. Rowland felt that much 

 progress could be made in this line of work if only larger and more 



