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XXIII. On the Water-Barometer erected in the Hall of the Royal Society. By 
J. F. Daniell, Esq. F.R.S . Professor of Chemistry in King's College , London. 
Read June 21, 1832. 
i HAVE for some time entertained an opinion, in common with some others 
who have turned their attention to the subject, that a good series of observa- 
tions with a Water-Barometer, accurately constructed, might throw some 
light upon several important points of physical science : amongst others, 
upon the tides of the atmosphere; the horary oscillations of the counterpoising 
column ; the ascending and descending rate of its greater oscillations ; and 
the tension of vapour at different atmospheric temperatures. I have sought 
in vain in various scientific works, and in the Transactions of Philosophical 
Societies, for the record of any such observations, or for a description of an 
instrument calculated to afford the required information with anything ap- 
proaching to precision. In the first volume of the History of the French 
Academy of Sciences, a cursory reference is made, in the following words, to 
some experiments of M. Mariotte upon the subject, of which no particulars 
appear to have been preserved. “ Le meme M. Mariotte fit aussi a l’obser- 
vatoire des experiences sur le barometre ordinaire a mercure compare au baro- 
mktre a eau. Dans Fun le mercure s’el&va a 28 pouces, et dans l’autre l’eau fut 
a 31 pieds Cequi donne le rapport du mercure a feau de 13^ a 1.” Histoire 
de l’Academie, tom. i. p. 234. 
It also appears that Otto Guricke constructed a philosophical toy* for the 
amusement of himself and friends, upon the principle of the water-barometer; 
* It consisted of a tube above thirty feet, rising along the wall, and terminated by a tall and rather 
wide tube hermetically sealed, containing a toy of the shape of a man. The whole being filled with 
water and set in a bason on the ground, the column of liquid settled to the proper altitude, and left 
the toy floating on its surface ; but all the lower part of the tube being concealed under the wain- 
scoting, the little image made its appearance only in fine weather. To this whimsical contrivance 
he gave the name of Anemoscope or Semper Vivum. 
