28 



Philosophical Character of Dr. Priestley 



abuse or encroachment which can possibly result, will not expose the 

 rights of the latter to material or important injury. 



There is still another consideration of great importance in favor 

 of this method which does not exist in the other. In all ordinary 

 cases the location of the boundaries may be determined without the 

 aid of the circumferentor, by means of the chain only. The great- 

 est error which can thereby result in the position of either boun- 

 dary, will not, exceed ten or twelve inches, supposing the offsets 

 to be made twelve degrees out of their proper direction, and in the 

 majority of cases will not probably exceed one third or one fourth of 

 that amount. 



The expense likewise, of this mode is at least forty per cent, less 

 than by the other, and when it is considered that the object to be at- 

 tained is effected in a much more perfect and scientific manner, it 

 must be conceded that it possesses a decided superiority. 



The mode of survey above described is alike applicable to rail- 

 ways as to Canals, and the description of it is thus publicly made, that 

 those who are engaged in the construction of works of inter-commu- 

 nication may avail themselves of the advantages which it possesses 

 over the less perfect methods ordinarily pursued in such cases. 



Middletown, Conn. Nov. 1832. 



— A 



stimate of the Philc 

 William Henry, M 



ofDr 



: 



f 



Read to the first meeting of the British Association, for the promotion of science, at 



York, September 23th, 1831. 



The principal source of the materials of the following pages, is 

 the work, in which the discoveries of Dr. Priestley were originally 

 announced to the public. It consists of six volumes in octavo, which 

 were published by him, at intervals between the years 1774 and 

 1786; the first three under the title of "Experiments and Obser- 

 vations on different kinds of Air;" and the last three under that of 



f 



" Experiments and Observations relating to various Branches of Nat- 

 ural Philosophy, with a continuation of the Observations on Air." 

 These volumes were afterwards methodised by himself, and com- 

 pressed into three octavos, which were printed in 1790. As a rec- 

 ord of facts, and as a book of reference, the systematized work is 

 to be preferred. But as affording materials for the history of that 



