academy of sciences] HYDRAULIC MINING DEBRIS 269 



The outlines of successive chapters prepared during Gilbert's convalescence at the "Her- 

 mitage'' in 1910 were superseded by new outlines a year later: 



I've had to change my point of view repeatedly and go back and rewrite. 



Progress was therefore slow not only because of short working hours but also because of 

 frequent revisions. A letter of January, 1912, gives an idea of the volume of computation 

 involved : 



In my work I have struck another stretch of computing and again the office has loaned me Mr. . 



His facility with the slide rule makes me wish I had lerned it years ago. It is rather late to train myself now, 

 and I am likely to stick to logs, as a mere matter of habit. Twice I tho't I would take it up and bo't a rule, 

 but it was always easier to do the next job in the familiar way than the new way, and I followed the line of 

 least resistance. But this present work has introduced me to log. section paper, and that has become quite 

 familiar. Of course, it involves the same principles as the slide rule. 



Then referring to the many different values of various factors that have to be computed, 

 he adds : 



Does it look attractive? Really it is not unattractive to me and I call for help only to save my own time. 



A month later he wrote: 



I am rather dismayed at the amount of computation that seems desirable; but it will probably pay to give 

 all my material a pretty thoro pre-digestion. 



In spite of the labor thus called for, Gilbert bore it better than he had ventured to hope 

 a year earlier. A letter of February, 1912, included a reassuring statement: 



I am working comfortably and stedily and must be increasing my average hours per day. In January I 

 reported — as the equivalent of my time in hours — 22 days, which is % of a full month. 



But this success was at the cost of declining outside efforts, as the following extract from 

 a letter of March, 1912, indicates: 



The President of the U. of R. [University of Rochester] directs my attention to the fact that the approaching 

 commencement is the 50th anniversary of my graduation, and invites me to give the commencement address — ■ 

 taking a scientific subject. Very sorry to have to decline. 



Computations were continued even during the summer on the New England coast, as 

 told in a letter of July: 



Work has gone slowly for a few days — staid on the mathematics of mean values, and had finally to go to 

 the library at Gloucester to get put on the right track. I find my equations and computations all right, but 

 I did not know how to put the theory of it into words. What cleared the matter up was a batch of definitions 

 in the Century Dictionary, and I found from the introduction that the mathematics of the C. D. was written 

 by C. S. Peirce — a man so metaphysical I should never have tho't of going to him with a practical question. 



Much time was taken by a phase of the work to which Gilbert, like certain other older 

 members of the survey, had not been accustomed to give much attention; for during the early 

 years of governmental surveys the practice of reading what foreign observers had accomplished 

 on problems similar to those attacked by our own geologists in the new western field had been 

 more honored in the breach than in the observance. But here it was dutifully followed, and 

 in the course of his work Gilbert made a much fuller examination of publications by British, 

 French, and German authors than he had ever made before. Indeed his manuscript was set 

 aside several times while foreign studies were searched out and read over, the aid of a foreign- 

 born member of the survey being sought on articles in French and German. A large amount 

 of pertinent matter was thus brought to his attention, although the main line of his own work 

 was on new ground. Sometimes he found himself lost in the modern terminology of physics, 

 as appears from a letter of October, 1912: 



When I have time I mean to read up on volts and amperes and such, to understand the gages [?] better than 

 I do. The electric units have all come in since my school days. 



Many books must have been consulted, for he wrote, in January, 1913: 



Still busy with the libraries, and found the French engineers have done some good work I did not know of. 

 Glad I did not go to print without finding out as to it. 



And a little later: 



Shall know right smart of hydraulics and some of hydrodynamics when I get thru. 



