1835.] Philosophical Transactions, 469 



The observations made by means of this instrument have confirmed 

 the accuracy of the results obtained in determining the place of any 

 star passing the meridian near the zenith. 



We have now three methods of observing this : 1st, By the mural 

 circles : 2nd, By the zenith telescope, used alternately east and west, 

 and 3rd, by means of a small subsidiary star. 



Geometrical Investigation concerning the Phenomena of Terrestrial 

 Magnetism. By T. S. Da vies. 



The present series of papers is chiefly intended to deduce the ma- 

 thematical consequences of the theory of two poles situated arbitrarily 

 within the earth, and especially to investigate the singular points 

 and lines which result from the intersection of the earth's surface 

 with other surfaces related to the magnetic poles, especially the points 

 at which the needle is vertical, the lines of equal dip, the Halleyan 

 lines, the isodynamic lines and the Hansteen poles. He investigates 

 at length the hypothesis of the duality of the terrestrial magnetic 

 poles, and shews that the question cannot be determined definitely 

 until the dipping needle is brought to a greater state of perfection 

 and the influence of geological and meteorological sources of distur- 

 bance can be accurately appreciated. 



Researches towards establishing a theory of the Dispersion of 

 Light. By the Rev. Baden Powell. 



For an abstract of this paper vide p. 147 of the present volume of 

 the " Records." 



Meteorology. 



On the Atmospheric Tides and Meteorology of Dukhun, (Deccan), 

 East Indies. By Lieut. -Colonel W. H. Sykes. 



This is a paper of great interest, as it contains a mass of facts 

 accumulated with great labour and care, in a portion of the world 

 where science, with the exception of botany, has hitherto been almost 

 unknown. The author, in the first instance, proceeds to describe 

 his instruments and his mode of proceeding to observation. These 

 are important points, and deserve an attentive consideration. The 

 proper mode of mounting meteorological instruments for observations 

 in tropical climates is particularly adverted to. Ivory scales and 

 reservoirs are proved to be useless ; the substitution of metals being 

 absolutely necessary. The conclusions to which the observations 

 lead are principally as follow : In the Dukhun four atmospheric 

 tides exist in the 24 hours ; two diurnal and two nocturnal, each 

 consisting of a maximum and minimum tide. These, as compared 

 with observations at the Royal Society, are 



Diurnal maximum fallinr^ 

 tide from 9 — 10 a.m. to 4 — 5 



P.M. 



Nocturnal falling minimum 

 tide from 10 — 11 p.m to 4 — 5 



A.M. 



Poonah . . — -0181 

 Royal Society —'0162 



Poonah . . — -1166 

 Royal Society — '0289 



