664 Lieutenant Eennt on the Constants of 



errors of barometric formulte ; not that I doubt that such errors are still very 

 serious, but I do not now believe them to be grievous to the extent I believed 

 them to be, when I prepared the Table of Errors (Table IV., page 639 of 

 this volume). For I am now aware that the said Table IV., page 639, has 

 been prepared from incorrect information, published by Monsieur E. Planta- 

 MOTJR in a scientific periodical, which appears in monthly parts at Geneva. It 

 is not for me to point out to Monsieur E. Plantamodr the mode in which such 

 periodical should be conducted, but, in justice to myself, I have to state my 

 regret that inaccurate information should have been thus given to the public, 

 whereby I have been led into a serious mistake concerning the mean-tempera- 

 ture errors of barometric formulas, and have been induced to occupy unneces- 

 sarily the time and attention of the Eoyal Irish Academy. It now appears 

 that the barometers of the Convent of the Great Saint Bernard and of the 

 Geneva Observatory have, each, a constant error, — the error of the barometer 

 of the Convent being 0'70 millimetres in excess ; that of the barometer of the 

 Geneva Observatory being 079 millimetres in defect. It also appears, that in 

 the scientific periodical published at Geneva, in monthly parts, under the 

 direction of Monsieur E. Plantamour, the constant error of the barometer of 

 the Convent has been applied to the published observations made at the Con- 

 vent since the year 1845, so that such published barometric observations are 

 correctly given ; but, unhappily, similar precautions have not been practised 

 in reference to the published observations of the Geneva Observatory, so that 

 such observations require a correction to the amount of 079 millimetres. 

 True it is, that once a year, near the middle part of the year, summer time. 

 Monsieur E. Plantamour publishes in the said scientific periodical, above 

 alluded to, a Resume, in full detail, of observations, barometric, thermometric, 

 hygrometric, &c., &c., &c., of the past year ; but seeing that I had no possible 

 opportunity of becoming acquainted with such Resume, I have,u nfortunately, 

 been employing incorrect data in working out my Table, No. IV., page 639. 

 Perhaps it may occur to some Members of the Academy, that although it did 

 not seem good to Monsieur E. Plantamour to apply the necessary correction 

 (viz., + 0'79°™') to the barometric observations made at the Geneva Observa- 

 tory, as he has done to those of the Convent Saint Bernard, — yet, surely, he has 

 not omitted, in each monthly publication, an intimation of some kind or other, that 



