Royal Society. 227 



fection of detail which nothing can surpass. To this process the 

 author applies the name of Chrysotype*, to recall to mind its analogy 

 with the Calotype process of Mr. Talbot, to which in its general 

 effect it affords so close a parallel \. 



2. "Experimental Researches on the Elliptic Polarization of 

 Light." By the Rev. Baden Powell, M.A., F.R.S., Savilian Pro- 

 fessor of Geometry in the University of Oxford. 



This paper contains an experimental'investigation of the pheno- 

 mena of elliptic polarization resulting from the reflexion of polarized 

 light from metallic surfaces, and the theory on which they are ex- 

 plicable ; the analytical results being given in a tabular form, and 

 applied to the cases of the experiments themselves. 



3. " On the Influence of the Moon on the Atmospheric Pressure, 

 as deduced from the Observations of the Barometer made at the 

 Magnetic Observatory at St. Helena." By Lieutenant J. H. Le- 

 froy, R.A., late Director of that Observatory. Communicated by 

 Lieut.-Col. Sabine, R.A., F.R.S. 



In order to determine the dependence of the barometric pressure 

 on lunar influence, the author arranges all the two-hourly observa- 

 tions in each lunar month with relation to the time of the moon's 

 passing the meridian; entering in one column the observation of each 

 day nearest to the meridian passage, whether before or after ; and en- 

 tering in separate columns those corresponding to two hours, four 

 hours, six hours, &c, before and also after that observation. The 

 monthly means at every two hours from the meridian passage are 

 then taken ; and again, the means at the same intervals, for each 

 three months from September 1840 to December 1841. From the 

 results thus obtained the author states that it appears that the moon's 

 passage over both the inferior and superior meridian produces a 

 slight increase of pressure ; a maximum in the curve occurring at 

 both (that of the latter being slightly the greater), while the minima 

 correspond to the moon's rising or setting. 



It appears also, that the rise of the tides will not account for the 

 whole amount of the increase of pressure, even admitting that it has 

 a tendency to produce an effect of that nature. The times of max- 

 ima do not correspond ; and there appears to be no atmospheric 

 establishment. The pressure is greater about the period of new 

 moon than at full moon ; and greater in the third and fourth than 

 in the first and second quarters ; a result which agrees with that 

 given by Mr. Howard for the climate of London. The observations 

 of both years agree in making the pressure greater under the Peri- 

 gee than under the Apogee. Mr. Howard had found that the mean 

 pressure in Great Britain, which is in the opposite hemisphere from 

 St. Helena, is greater under the Apogee than under the Perigee. 



4. " Notices of the Aurora Australis from the 1st to the 31st of 



» Note by the Author. — A solution of silver produces a like effect, and 

 with greater intensity, but much more slowly. Consequently the name 

 Chrysotype would seem less appropriate than Siderotype. — J. F. W. H. 



[f Mr. Talbot's account of his Calotype process appeared in Phil. Mag., 

 Third Series, vol. xix. p. 88, 164 — Edit.] 



Q2 



