178 



whether any coincidence of period or epoch is traceable. Now the 

 facts of the solar spots, as they have been recently made known to 

 us by the assiduous and systematic labours of Schwabe, present us 

 with phenomena which appear to indicate the existence of some 

 periodical affection of an outer envelope, or photosphere, of the sun ; 

 and it is certainly a most striking coincidence that the period, and 

 the epochs of maxima and minima, which M. Schwabe has assigned 

 to the variation of the solar spots, are absolutely identical with those 

 which have been here assigned to the magnetic variations." From 

 the results of his observations of the solar spots from the years 

 1826 to 1850, M. Schwabe has derived the conclusion that "the 

 numbers in the table leave no room to doubt that, at least from the 

 years 1826 to 1850, the solar spots have sho"\vn a period of about 

 ten years, with maxima in 1828, 1837, and 1848, and minima in 

 1833 and 1843." M. Schwabe has not been able to derive from the 

 indications of the thermometer or barometer any sensible connection 

 between climatic conditions and the number of spots. The same 

 remark w^ould of course hold good in respect to the connection of 

 climatic conditions with the magnetic inequalities, as their periodical 

 variation corresponds v/ith that of the solar spots. But it is quite 

 conceivable that affections of the gaseous envelope of the sun, or 

 the causes occasioning those affections, may give rise to sensible 

 magnetical effects at the surface of cur planet, without producing 

 sensible thermic effects. 



May 13, 1852. 



WILLIAM SPENCE, Esq., V.P., in the Chair. 



The following communications were read : — 



1, "Report of the general process adopted in Graduating and 

 Comparing the Standard Meteorological Instruments for the Kew 

 Observatory." By Mr. John Welsh. Communicated by Col. Sabine 

 on the part of the Committee of Recommendations of the Govern- 

 ment Grant. Received May 6, 1852. 



In offering to the Committee a short statement of the progress 

 made at the Kew Observatory in the construction and verification 

 of thermometers, I shall first describe generally the method pursued 

 in the graduation of standard instruments. 



The plan of operations hitherto adopted has been that proposed 

 by M. Regnault, and consists essentially of the following steps : — 

 1st. Calibration of the tube : 2nd. Graduation of the scale : and 

 3rd. The determination of the scale coefficients. 



1 . CaUhration. — A tube having been selected as being tolerably free 

 from all visible defects, a short column of mercury, generally less 

 than one inch in length, is introduced. The tube is then attached 

 to the frame of Perreaux's dividing- engine, and by means of flexible 

 tubing is put in connection at both ends with india-rubber bags, the 

 pressure upon which can be regulated by means of screws. The 



