110 . Twenty-Second Annual Report on State Cabinet. 



repeated observations, 2° 40' west. It was suspected that a slight 

 local attraction was due to the rock, but this being a constant, would 

 not affect the accuracy of subsequent comparative observations at 

 that place. 



Holland Land Company's Purchase. 1798-9. 



The original field books of this survey are, by law, deposited in 

 the Secretary's office at Albany for preservation, and afford about a 

 hundred and forty observations of magnetic variations, with the dates 

 of observation, names of surveyors, and place, as designated by ranges 

 and lot lines. This survey was made under the general direction of 

 Mr. Joseph Ellicott, an engineer of excellent reputation. We have 

 no record of the methods by which the true meridian was ascertained, 

 nor of the accuracy of the instruments or the care with which the 

 variation was ascertained. 



Concerning the uncertainties arising from this cause, Mr. Ellicott, in 

 a semi-official document prepared as an explanation of his surveys, 

 remarks : 



" The difference that is discernable in the size of the several 

 townships is occasioned by the variation of the needle, which, from 

 certain occult causes, is found to differ essentially between any two 

 stations that may be fixed on, and much more between some stations 

 than others. Hence, in taking the magnetic courses of any two town- 

 ships, it will follow that a disproportion in size of the several town- 

 ships will necessarily arise, as the needle is seldom, known to preserve 

 a uniform position between places but a few hundred yards from 

 each other ; so that inaccuracies will arise though the greatest circum- 

 spection should be observed in correcting courses." 



This survey was made by ranges and townships. The ranges were 

 numbered from the east line of the tract towards the west, and were fif- 

 teen in number. The townships were numbered from the State line 

 of Pennsylvania northward to Lake Ontario, and extended to sixteen 

 in number. The accompanying map will exhibit the lines of the 

 original townships and the corresponding divisions by towns and 

 counties, as now organized. 



