GKOLOGICAL AND NATUllAL HISTOIIY SURVEYS. 49 



Percival's account of his metliods of procedure are not without in- 

 terest. He says : ' 



I had twice surveyed the whole State ou a regular plan of .sections from east 

 to west, reducing the intervals in the last survey to an average distance of 2 

 miles, thus passing along one side of each of the nearly 5,00<) square miles of 

 the State. * * * x had examined all objects of geological interest, particu- 

 larly the rocks and those Including minerals, with minute attention. I scarcely 

 passed a ledge or point of rock without particular examination. I had com- 

 pleted 11 manuscript volumes, amounting to nearly 1^500 pages, very finely writ- 

 ten in abbreviation. I had collected specimens from at least 8,000 locrdities, 

 according to a very reduced calculation from actual enumeration of one town, 

 and several specimens from each locality, each specimen intended to illustrate 

 something peculiar and noticed in my notes; all my specimens marked on the 

 papers enclosing them and checked in u)y notebooks, so that I know their precise 

 locality and could again trace them to the spot where I found theni. In all 

 these researches, from the commencement, I had had in view the determination 

 of the geological system of the rocks of the State. All these researches had 

 been a continued process, not only of particular examination, but of comparison 

 and reflection, all tending to the determination of the great system. I say with 

 the confidence of conviction — of that conviction which arises from long-con- 

 tinued devotion to the subject — that I have determined in my mind the system 

 of arrangement; that it is a new system with me, the result of my own un- 

 assisted observation, one which I have not traced in my reading, and one which 

 I believe to be of the highest importance, not only to science, but for economical 

 purpose.s. * « * Besides this more general plan of the survey, I had espe- 

 cially explored and traced out the trap, both connected with the primary and 

 secondary, and determined a new and important system of arrangement, ap- 

 parently applicable to both, and one, too, of which I have found no traces in my 

 i-eading. « * * 



Up to the session of J840, I liad employed five years on the survey and had 

 received $.'>,000, averaging $600 per annum, out of which I had defrayed all 

 expenses, traveling expenses included. * * * i ^y^s then required to prepare 

 a report, cut off from all resources, deprived of that pittance of $500, which I 

 might have secured two years before almost without additional labor, if I had 

 regarded my own interests only. 



According to Professor Dana,' Percival, on entering upon his 

 (iuties, saw before him two great problems : 



First, the character and origin of the trap ridges of the State, such as East 

 and West Rocks near New Haven, the Hanging Hills of Meriden, and other 

 similar heights to the north and south, * <» * and, secondly, the characters 

 and origin of the granitic series of rocks wliich prevail through all the rest of 

 the State. 



Percival's observations proved : 

 that there had been not one long-continuous fractni-o through the State from 

 New Haven to the regions of Mt. Tom and beyond, for the injection of liquid 

 trap rock, but instead, a series of openings along a common line, and that there 

 were .several such lines running a nearly parallel course over a broad region 

 of country. He also found that the ridges which compose a range do not 

 always lie directly in the same line, but that often the parts which follow one 



» Life and Letters of J. G. Percival, by J. IT. Wood. 



