TRANSACTIONS OF THE SECTIONS. 



61 



C'est a I'occaslou des travaux que j'ai executes aSantorin en 1867, que j'ai iuia- 

 giue ce therinometve pour prendre la temperature de I'eau de la nier pres du 

 volcan alors en activittS. 



Je m'en suis servi daus un voyage aux Azores en 18G7, depuis Lisbonne jusqu'a 

 St. Michel. 



Je I'ai (Sgalement employf^ dans mes deux Toyages aux Indes en 1863 et 1871. 



Or j'ai constamment controle les indications du thermometre a pinceau en pre- 

 nantles temperatures par la niethode ordinaire, qui consiste, comme on salt, a puiser 

 directement dans la uier un seau d'eau dans lequel on place uu thermometre. Les 

 deux methodes se sont toujours accordees a -jL de degvo quaud on operait avec le 

 soin necessaire. 



A ma demande, M. Giraud, officier de marine fran^ais, a bien voulu prendre des 

 temperatures de la Mediterran(5e pendaut plusieurs voyages de Marseille a Alex- 

 andrie. Get officier avait aussi le soin de controler les indications du thermo- 

 metre a pinceau jete a la mer par celles que le nieme instrument depouille de son 

 pinceau donnait daus un seau d'eau puise au meme iustant. 



On donne un fragment de ses resultats, p. 60. 



En resume, le thermometre a pinceau a tres-hien soutenu de nombreuses epreuves 

 depuis cinq annees, et on pent le considerer comme un instrument acquis a la science. 



On en construit beaucoup en France. 



On the Temperature-correction of an Aneroid. Bij John Phillips, M.A. and 

 Hon. D.C.L. Oxon., F.E.S., Professor of GeoJogy in the University of Oxford, 



Few instruments invented in modern days have found a more ready and general 

 acceptance for ordinary observations of atmospheric pressure than the Aneroid ; 

 but for accurate weighing of the column of air it is not to be trusted without care- 

 ful precautions, and a preliminary study of the particular instrument emploj^ed. 

 The object of this communication is to explain a method by which an instrument 

 which has been in frequent use for nine years, and is liable to enormous variation 

 of reading by change of temperature, has been made to give accurate results. 



The instrument has a diameter of 1-9 incli, and weighs 1560 grains. It is quick 

 and firm in its indications while kept in the same position and at the same tem- 

 perature : but the reading is reduced if the position be changed from horizontal to 

 vertical, and by any, however small, elevation of temperature. It has suffered 

 many shocks, but is entirely uninjured by these and other misfortunes. Though 

 divided only to ^V i^ich, its indications can be recorded with entire confidence to 

 24o ) and are, in fact, by a peculiar method of reading, written down by estimation to 

 ■x-ias- Its scale is correct for a range of 24 to 31 inches. 



Held in the warm hand, or exposed to sunshine, the index turns sensibly to the 

 left. Heated from 40° to 80°, the deviation exceeds three tenths of the baro- 

 metric inch. By employing a hot closet the effect is augmented enormously, so 

 that for one degree at 100° Fahr. the index retreats about -020 inch. 



After numerous and often-repeated comparisons with a standard barometer, at 

 different atmospheric pressures and temperatures, the following summary of ob- 

 served differences or corrections (e) to be applied to this aneroid, so as to make its 

 indications agree with the mercurial instrument, as read at the same time, was 

 adopted as a basis for calculation. The corrections are additive. 



1872. 



