406 Proceedings of the British Association. 



tial and final co-ordinates, and the intervening time ; and, lastly, 

 in the problem of three bodies. 



Professor Phillips communicated a paper on a new form of the 

 Dipping Needle, constructed so as to afford the means of correct- 

 ing the error of the centre of gravity. 



Colonel Sykes read a short paper entitled, Notes on the mean 

 temperature in India, which called forth some remarks from Sir 

 David Brewster and Professor Forbes. 



Professor Lloyd gave an account of magnetical observations 

 undertaken in Ireland in pursuance of the recommendations of the 

 Association ; and of a new method of observation which he had 

 employed. 



Dr Robinson stated to the meeting various objections to the site 

 of the present Observatory of Edinburgh, and suggested the pro- 

 priety of transferring that Observatory to some more suitable posi- 

 tion ; and of converting the existing building to the purposes of a 

 magnetical observatory. Dr Robinson concluded by stating the 

 proposition which he intended to submit on this subject to the Com- 

 mittee of the Section. Sir David Brewster also stated the result 

 of his own observations on the progress of destruction now going 

 forward in the object-glass of the transit instrument. 



M. Arago made some remarks on the accuracy which may be at- 

 tained in usual methods of observing the dip of the magnetic needle. 

 He stated that, when the instrument was furnished with a micro- 

 meter, and the necessary cautions observed, he found it adequate 

 to the determination of the diurnal variation of the dip, contrary 

 to the opinion expressed by Professor Christie in his report on 

 terrestrial magnetism. M. Arago also stated the results of some 

 observations of his own on the decay of the object-glasses of te- 

 lescopes. 



Professor Forbes read a short communication from Mr Jordan, 

 describing a mode of suspending the magnetical needle, which it is 

 supposed by the author would possess some advantages for observ- 

 ing variations in the direction and intensity of the earth's magnetism. 



Sir David Brewster described to the meeting a remarkable co- 

 loration which he had observed in the space included between the 

 interior and exterior rainbow. 



Mr Saumarez read a paper on light and colours, containing some 

 peculiar views respecting their nature and origin. 



