624 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 30 



of rocks. It was along these lines that Merrill's greatest activity 

 lay between 1881 and 1905, and during these years he published 

 upwards of 80 papers and books, a total of 40 per cent of his entire 

 bibliography. 



The reason for Merrill's entering the field of petrology he tells 

 as follows : 



My abrupt shift from chemistry to geology was due purely to a newly-made 

 friendship with Doctor Hawes who was at that time one of the leading 

 authorities on microscopic petrology, a branch of study then just coming into 

 vogue. It was understood at the time of my accepting this position [in the 

 National Museum] that, there being no university in America where this 

 branch of geology could be studied, I should be assisted in taking it up by 

 Doctor Hawes, but unfortunately, owing to his failing health, this part of 

 the agreement was never carried out. At the time I became Doctor Hawes's 

 assistant he had been appointed a special agent of the Tenth Census, in charge 

 of the building-stone industry, his idea being to ascertain not merely the mag- 

 nitude of the industry, but as well the petrographic characters of the mate- 

 rials. It was in the latter branch of the work that I was engaged. (MS. 

 1924.) 



With the death of Hawes this study and the completion of the 

 report fell to Merrill and he made good use of his opportunities, as 

 the Tenth Census report shows. (1884b.) Before this study was 

 completed Merrill further prepared himself in petrology at Johns 

 Hopkins University, where the subject had been developed by Prof. 

 George H. Williams, 



Merrill's first duty in the Museum was the cutting of thin sections 

 of the entire collection of some 4,000 samples of building stones that 

 had been brought together from upward of 1,500 quarries in the 

 United States, together with manj^ from foreign countries — " the 

 most systematic and complete collection of its kind in any museum 

 in the world." Each specimen was examined under the micro- 

 scope " in order not only to determine what the rock was, but also 

 to ascertain if it contained any mineral constituents liable to un- 

 favorable change on exposure to the weather." (1885a: 521.) 



As the Government hours were but from 9 a. m. to 4 p. m., I had opportunity 

 to study and all encouragement in the way of use of the materials, and with 

 Hawes' volume on the petrography of New Hampshire and Zirkel's report on 

 the fortieth parallel rocks, together with the first edition of Rosenbusch's 

 Mikroskopische Physiographie, I proceeded to equip myself as best I might. 



The final report, by 21 authors, contained an introductory treatise 

 by Hawses on micropetrology, followed by Merrill's account of the 

 mineral nature and microstructure with illustrations, and was issued 

 as a part of volume 10 (1884b: 15-29) of the publications of the 

 Tenth Census. 



The 18 artotype reproductions of photographs taken through the microscope 

 were the best that had thus far been reproduced. 



This work on building stones naturally led to his first book, The 

 Collection of Building and Ornamental Stones in the United States 



