S78 Royal Society : Dr. Stark on the supposed 



determination of the declination and inclination of the needle, the 

 horizontal and total magnetic intensity deduced from the observa- 

 tions at thirty-two stations, of which the latitudes and longitudes 

 are given in the same table, together with the dates of observation. 

 May 25. — The following papers were read, viz. — 



1. "Meteorological Journal, from January to April inclusive, 

 1843, kept at Guernsey." By Samuel Elliott Hoskins, M.D. Com- 

 municated by Samuel Hunter Christie, Esq., Sec. R.S. 



2. " On the Respiration of the Leaves of Plants." By William 

 Hasledine Pepys, Esq., F.R.S. 



The author gives an account of a series of experiments on the 

 products of the respiration of plants, and more particularly of the 

 leaves ; selecting, with this view, specimens of plants which had 

 been previously habituated to respire constantly under an inclosure 

 of glass ; and employing, for that purpose, the apparatus which he 

 had formerly used in experimenting on the combustion of the dia- 

 mond*, and consisting of two mercurial gasometers, with the addi- 

 tion of two hemispheres of glass closely joined together at their 

 bases, so as to form an air-tight globular receptacle for the plant 

 subjected to experiment. 



The general conclusions he deduces from his numerous experi- 

 ments conducted during several years, are, first, that in leaves which 

 are in a state of vigorous health, vegetation is always operating to 

 restore the surrounding atmospheric air to its natural condition, by 

 the absorption of carbonic acid and the disengagement of oxygenous 

 gas : that this action is promoted by the influence of light, but that 

 it continues to be exerted, although more slowly, even in the dark. 

 Secondly, that carbonic acid is never disengaged during the healthy 

 condition of the leaf. Thirdly, that the fluid so abundantly exhaled 

 by plants in their vegetation is pure water, and contains no trace of 

 carbonic acid. Fourthly, that the first portions of carbonic acid 

 gas contained in an artificial atmosphere, are taken up with more 

 avidity by plants than the remaining portions ; as if their appetite 

 for that pabulum had diminished by satiety. 



3. A paper was also in part read, entitled " On the minute Struc- 

 ture of the Skeletons or hard parts of the Invertebrata." Part II. 

 By William B. Carpenter, M.D. Communicated by the President. 



June 1. — The following papers were read, viz. — 



1. "Magnetic-term Observations for January, February, March, 

 and April 1 843," made at the Observatory at Prague, by Professor 

 Kreil. Communicated by Samuel Hunter Christie, Esq., Sec. R.S. 



2. " Hourly Meteorological Observations, taken between the 

 hours of 6 a.m. March 17th, 1843, and 6 a.m. of the following day, 

 being the period of the Spring Tides of the Vernal Equinox, at 

 Georgetown, British Guiana." By Daniel Blair, Esq., the Colonial 

 Surgeon, transmitted by Henry Light, Esq. Communicated by the 

 Lords Commissioners of the Admiralty. 



[* The paper in which this apparatus is described was inserted in Phil. 

 Mag. S. 1. vol.xxix. p. 216.] 



