﻿Mr. B. Stewart on certain Experiments on Aneroid Barometers. 71 



We see from these results, if aneroids, right to begin with, be 

 subjected to a decrease of pressure similar to that to which they were 

 subjected in these experiments : — 



(1) That a well-constructed large aneroid will not go far wrong 

 down to 24 inches ; but after that pressure its reading will be consi- 

 derably lower than that of a standard barometer, so that a large 

 positive correction will have to be applied. 



(2) That small aneroids are less trustworthy than large ones, and 

 probably cannot be trusted below 26 inches. 



(3) That if previous experiments are made upon an aneroid, we 

 are enabled by this means to obtain a table of corrections which, 

 when applied to future observations with the same instrument, will 

 most probably present us with a much better result than had we not 

 verified our instrument at all, and that by this means we may use 

 our instrument down to 19 inches with very good results. 



Let us now consider the up readings of these instruments, and let 

 us suppose that each instrument is right to begin with — that is to 

 say, while remaining an hour and a half at its lowest reading. 



These corrections and up readings are exhibited in the following 

 Table :— 



Table III. 



No. of 



Correction for the up readings of the aneroids of Table I. supposed right 



with standard at lowest reading. 



ane- 

 roid. 























19 m. 



2,0 m. 



21 m. 22 m. 



23 in. 



24 in. 



25 in. 



26 in. 



27 m. 



28 in. 



-•08 



29 m. 



30 in. 



8. 



•00 



+•03 



+ •03 4- -05 



H--os 



+ •02 



+ •01 



-•03 



-•04 



— •11 



-•18 



9- 



•00 



4-05 



4--o6 



4--o6 



+•04 



+ •06 



4--o6 



+ •05 



+ •05 



4--oi 



-•02 



— "C2 



8. 



•00 



+ ■02 



4--oi 



■00 



4"'C2 



— •01 



-•03 



-•06 



— •11 



-•15 



— •16 — '19 



9- 



•00 



+ •03 



+ •03 



— •01 



+•01 



+ •02 



4-'o2 



+ •04 



•00 



-•03 



-•06 



-•OO 



IO. 



•00 



•00 



+ •03 



+ •04 



+•03 



4- ' 07 



+ -os 



4"*C2 



•00 



-•05 



— •08 



— 'II 



1 1. 



•00 



-•04 



— •02 



•00 



-■03 



-•os 



-•08 



— "II 



-•14 



-•13 



-•16 



-•14 



12. 



•00 



+ •01 



— •02 



— •02 



— •1 I 



— •12 



— •12 



-•14 



— •21 



— •20 



-•24 



-•26 



13- 



•00 



+ •05 



+•05 



+•06 



+ 'c<; 



+ 'os 



+ •05 



+•05 



+ -o S 



— •01 



— 'ii 



-•14 



14. 











•00 



+ •09 



4-*i2 j4-*i2 4--ii 



+ •07 



+ -03 



4"'02 



15. 











'OO 



— •01 



-•06 --o6|--o8 



-•09 



-•06 



-•08 



16. 











•00 



4"*02 



+•03 



•co —'03 



-•04 



-•07 



-•06 



17. 











•00 



4--oi 



-02 



-•04 1 — -II 



-•19 



-•28 



-'33 



Hence we find the mean up correction for large aneroids :- 





19 m. 



20 in. 



2 1 in. 



4- -03 



22 in. 



23 in. 



24 in. 



25 in. 



26 in. 



27 m. 



28 m. 



29 m. 



30 m. 



Supposedrigbt 

 at 19 in 



•00 



+ •03 



+•03 



+ •03 



{-'02 



+ •01 



•00 



-•03 



-•06 



-•08 



— 11 



Supposedright 

 at 23 in 











•00 



+ •04 



+ •03 



+ •03 



+ •01 



— •01 



— •02 



-•03 



