249 



Exercises Pratiques d" Analyse, de Syntaxe, et de Lexigraphie Chi- 



noise. Par Stanislas Julien, Professeur au College Royal, &c. 



8vo. Paris, 1842. — From the Author. 

 Statement of Deaths, with the Diseases and Ages, in Philadelphia, 



during the year 1841. Published by the Board of Health. — 



From Mr. Samuel P. Marks. 



Professor Bache announced the death of the Hon. Samuel 

 L. Southard, a member of the Society, on the 26th June, 1842, 

 aged 56. 



Professor Bache described a dew-point hygrometer, the 

 principle of which he believed had not been before applied to 

 that instrument. A surface, of which the different points are 

 at different temperatures, some above, and others below the 

 dew-point, is exposed to the deposition of moisture; and the 

 dew-point is indicated on this, by the temperature of that point 

 at which the deposit ceases. 



Several forms of the instrument were noticed. One for the pur- 

 poses of an observatory, consists of a steel bar, one extremity of 

 which fits into a tube passing through a metallic or a wooden box. 

 The bar is pierced at regular intervals from the box with small cylin- 

 drical holes, passing vertically downwards from the upper surface of 

 the bar to points below its axis, and intended to receive the bulb of 

 a delicate thermometer. The temperature of the end of the bar 

 within the box being reduced by cold water, ice, or a freezing mix- 

 ture, the heat is gradually drawn from the part without. When equi- 

 librium is attained, and the deposit of dew reaches a fixed position, 

 the temperature of the bar at the dew line is ascertained, either di- 

 rectly by the thermometer, if the dew line corresponds with the axis 

 of a cylindrical hole, or else by observing the temperatures of 

 the holes on each side, and thus obtaining the temperature of the 

 dew line, by a proportion. The intervals not being greaf, the curve, 

 whose ordinates would represent the temperatures, the abscissae being 

 the distances from the extremity of the bar, may be taken as a straight 

 line. Or, if more minute accuracy is sought, the bar may be pushed 

 into the box until the section of deposition reaches the axis of a cy- 

 lindrical hole. A copper bar, with gilded surface, may be used with 

 advantage in certain cases, but does not present so beautifully defined 

 a line of dew as the steel bar. Professor Bache spoke of the import- 



