1826.] On the Measurement of Heights hy One Barometer. 368 



Article VI. 



Heply to Mr. Herapath. By W. G. Horner, Esq 



(To the Editors of the Annals of Philosophi/.) 



GENTLEMEN, Balk, jipril 2, 18S6. 



On the subject of Mr. Herapath's reply, contained in your 

 last Number, I beg leave to explain, that any charge of inten- 

 tional fallacy was far from my thoughts. Whether I have been 

 guilty of misrepresentation, or advanced a groundless charge, I 

 cheerfully leave to our readers' decision. 



I am, yours, &c. W.G.Horner. 



Article VII. 



On the Accuracy of the Measurement of Heights by One Baro- 

 meter. By J. Nixon, Esq. 



(To the Editors of the Annals of Philosophy.) 



gentlemen, Leeds, Apnl&, 1826. 



Presuming that the comparison of heights measured as well 

 trigonometrically as by one barometer might prove interesting to 

 some of your readers, I have taken the liberty to transmit you 

 the following list, computed from observations made in 1822 to 

 1825 inclusive. 



The barometers employed, of the description invented by Sir 

 H. Englefield, were four in number, viz. 



One by Troughton, capacity ■^, marked T in the table. 



DoUond ^'y D 



Newman ^ N 



Ditto (iron cistern) ^y . I 



Unknown ^ U 



With regard to the measurements by the first two mentioned 

 instruments, undertaken solely with a view to ascertain that no 

 gross errors had been committed in the trigonometrical observa- 

 tions or calculations, and of which nearly one-half were entrusted 

 to the guides, &c. it must be remarked that little of the attention 

 requisite to insure extreme accuracy was devoted to the gene- 

 rality of the observations. Inapplicable as is the remark to the 

 measurements by the other barometers, which were for purposes 

 of geology, and made with excessive care, it becomes necessary 

 to state, in order to inspire increased confidence in measure- 

 ments of this description, that there was no selection of those 

 favourable circumstances of pressure, temperature, &c. so essen- 



