academy of sciences] HYDRAULIC MINING DEBRIS 275 



WORK UPON SECOND REPORT 



Gilbert's letters confirm the impression of his deep interest in this phase of his report that 

 a reader gains in looking it over. He was at work upon it in the winter of 1913-14 in Wash- 

 ington, when a letter to his son tells of liis progress: 



I find the working up of the tidal-prism problem in the bays mighty interesting — but I lost two days work 

 by starting in with a bad theory. Then when I straitend that out I found I needed more data than hav been 

 publisht. I tho't however that the additional data were in existence & by going over to the Coast Survey 

 was able to get them. I also told my revised theory to the tidal expert — Harris — and was reassured that I was 

 on the right track. 



The pleasure afforded by the work on the bay was referred to again later: 



Tide problems continue to be fascinating. Hav been especially attractiv this week because I've studied 

 out a tangle that was bothering me. 



He wrote in March, 1914: 



I've been occupied for several days in measuring areas of lakes and tidal lands, and now am compiling a 

 map to show all tracts affected by the Golden Gate tides. . . . My compilation is very ruf, so as to get the whole 

 thing where I can see it in a bunch, but I mean to hav a careful compilation made for printing. I find the prob- 

 lem of the effectiv tidal prism a fascinating one. Did I ever show you my reticle for estimating areas? It is a 

 plate glass slab, with a half -inch mesh engraved on one side. Laying it over a map I estimate an area by units 

 of the mesh. For the rougher work I count the units which are more than half on the tract to be measured. 

 For finer work I estimate by eye to the tenth of a unit. 



Few other subjects were allowed to interrupt these studies of debris and tides; but in 

 March, 1914, a proposed side issue naturally proved irresistible: 



There is a temptation on my table — to interrupt my regular work to do an attractiv thing which will take 

 only a few days. I am requested to write a chapter on Lake Bonneville and Great Salt Lake for a railway 

 guide to be issued by the Geological Survey for tourists to the Panama Exposition [in San Francisco, 1915]. 

 I'd like immensely to do it, but feel that I ought to stick to this mining debris report till it is finisht. So I am 

 tempted and hesitate. 



But in the end he wrote the desired chapter. 3 



The enlarged understanding of the tides in San Francisco bay that came while Gilbert 

 was still occupied in Washington with the "fascinating study" of the effective tidal prism 

 naturally led to a more critical study of the tides in the bay itself ; hence when he went to Cali- 

 fornia in the summer of 1914 he did not as before make the Faculty Club at Berkeley his head- 

 quarters, but took a room at the University Club in San Francisco. Soon after arriving there, 

 he wrote to one of his sons: 



Yesterday, Mr. and I did some work on the tides . . . spending the day in a boat. Am elaborately 



sunburnt. Have cald this morning on ... to arrange for an observer to supplement next Saturday 



in the Golden Gate. The job will take about 30 hours and I cannot depend on myself — and of course one ob- 

 server cannot take the whole stunt. ... I was at the Faculty Club last week and saw a lot of people we know. 

 Had a game of billiards and of bridge. 



Half a year later, proof reading became for a time about as great a burden as computation 

 had been before. 



The rest of the book proof has come — 187 galleys in all, and it will be the middle of the week before I am 

 thru with it. I hav to go slowly — becaus careless reading is sure to leav blunders undetected. Most of the 

 things I find to correct are slips of typists or compositors, but some of them are my own — and that's saddening 

 for I went over the manuscript many times. I can not hope to eliminate all now, but am doing my best. 



This fatiguing duty continued to March, 1915: 



Not thru with my proof yet. Find it pays to read the whole thing again— keep discovering things I should 

 be mortified to detect after publication. Think of letting "a phenomena" pass me several times in the dm. 

 and twice in proof! And yesterday I discovered a rather important statement from which the word "not" 

 had been omitted. 



» U. 8. Qeol. Surrey, Bull. 612, 94-99. 



