198 PROCEEDINGS OF THE AMERICAN ACADEMY 



in wbicli there is no evidence of law. Examples were given of all 

 these various peculiarities. 



" In the second portion of the memoir, the mental time-scales by 

 which different observers subdivide the second were subjected to analy- 

 sis, and the extraordinary gain to science which has accrued from the 

 American method of observation was carefully discussed. The time- 

 scale of each observer was inferred from the relative, number of times 

 which each tenth of a second occurred in his observations. It was 

 shown that the habits of the observer were invariable in this respect, 

 and were not subject to change with time or circumstance. It was 

 also shown that the reference of this peculiarity to the inequality of the 

 time-scale was the only just and consistent theory. It appears that, 

 although some of the oldest and most experienced observers, such as 

 Henry and Main of the Greenwich Observatory, are peculiarly prone 

 to excessively defective time-scales, from which the younger observers, 

 such as Ellis, Dunkin, and Rogerson of Greenwich, and Keith and 

 Almy of Washington, are comparatively free, yet the veteran Arge- 

 lander manifests, in this respect, the great superiority of his training. 

 But with the American method the irregularity of time-scale vanishes, 

 and in this first step with which America has commenced its astro- 

 nomical career, we must, when we examine it historically and critically, 

 claim to recognize the future promise of the country in this science, 

 when the field shall be fairly opened. The American method is the 

 unquestionable product of the Coast Survey of the United States, and 

 was the legitimate result of the rigid and profound methods of research 

 which are uniformly adopted in this magnificent work. The first con- 

 ception was in the mind of the Superintendent himself. Professor 

 Bache, and its complete development and ultimate success were owing 

 to the united action of Professor Bache and his friend and assistant, 

 Mr. Sears C. Walker. The details of the instrumental invention and 

 execution were intrusted to Messrs. Saxton, Bond, Mitchel, and Locke. 

 Difierent plans were proposed, but that of Mr. Bond is the one which 

 is at present adopted in the Coast Survey, although some of the others 

 possess peculiar advantages, Avhich deserve further examination and 

 experiment. The ingenious apparatus which has been adopted by 

 Professor Airy, at Greenwich, differs radically from either of the 

 American forms, although this distinguished astronomer candidly ad- 

 mits the American origin of the method, and states distinctly that ' the 



