298 Captain Sabine's comparison of barometrical and 
apparently uninjured. I had with me a third barometer 
made by Mr. Newman for a Gentleman at Hammerfest, at 
the same time and with equal care as the others, and which 
had been compared with them in London : by means of the 
third barometer the alteration was ascertained to have taken 
place in Mr. Jones's, and not in either of Mr. Newman's. 
It has since occurred to me, as affording a possible explana- 
tion of the alteration, that after the comparison in London, 
Mr. Jones took his barometer with him to his house to en- 
grave the neutral point, and the diameter of the tube, upon 
the brass cover of the cistern, and I remember that he 
spoke of one or two screws which required to be tightened, 
and which, he observed, might affect the relation of the 
cistern and scale. That the alteration should have taken 
place at that time and in some such manner ; and that the 
mercury which appeared between the cistern and its cover 
had lodged there accidentally in the original putting toge- 
ther of the instrument, and that it was not therefore con- 
cerned in producing the change, would seem the more 
probable supposition, than that it should have escaped subse- 
quently from the cistern ; since, if a part of the mercury had 
found a means of escape, more would have followed either 
then or since, which however has not been so, as no altera- 
tion has taken place subsequently in the relative indications 
of the two barometers. Having ascertained this last fact on 
my arrival at Spitzbergen, in July, a careful series of compa- 
risons was instituted to determine the exact amount of the 
alteration since the original comparison at Mr. Newman's, 
and to obtain a fresh index correction and neutral point, since 
each would be alike affected, whether the cause were a 
