Proceedings of the British Association. 155 



Master-General of Ordnance has ordered a second officer of Ar- 

 tillery, (Lieut. Clerk,) to be attached to the observatory at the 

 Cape of Good Hope. 



The magnetic survey of British Guyana has been undertaken 

 by Mr. Schomburgk, one of the commissioners appointed by Gov- 

 ernment to determine the boundaries of that province. The Af- 

 rican Expedition has also been supplied, by Government, with the 

 necessary instruments for observation. From the scientific zeal 

 which distinguishes many of the officers of that expedition, scarce- 

 ly inferior to that zeal in the cause of humanity which has led 

 them to enter on so perilous a service, results highly valuable to 

 magnetic science may be expected. 



Mr. Caldecott, astronomer to his Highness the Rajah of Tra- 

 vancore, has also declared his intention to undertake the magnetic 

 survey of Southern India ; while in the north of that empire we 

 may expect, from the zeal and energy of Capt. Boileau, that no 

 exertions on his part will be wanting to secure a similar advan- 

 tage in that quarter. 



In all such surveys, it is highly desirable that a regular and 

 concerted system of observation should be followed, and above 

 all things that the condition of exact conformity to the hours of 

 simultaneous observation should be adhered to ; as well as that, 

 if practicable, all determinations of important points, intended to 

 be made with particular care and exactness, should be performed 

 on the term-days ; which object, by the exercise of a certain de- 

 gree of forethought in laying out the plan of travel, may doubt- 

 less be accomplished in the great majority of instances. 



The President submitted a series of curves, prepared by Lieut. 

 Riddell, representing the simultaneous changes of the magnetical 

 elements, observed at Toronto, Dublin, Brussels, Prague, Milan, 

 St. Helena, and Van Diemen's Land, on the 29th of May and 

 29th of August, 1840. He remarked that one of the chief ob- 

 jects kept in view in the arrangement of the great system of com- 

 bined observation now in operation, was the extension of the plan 

 of simultaneous observations at short intervals of time, first laid 

 down by Gauss. The results of this system had been, that the 

 observed changes of the magnetical elements were strictly simul- 

 taneous at the most remote stations at which observations had 

 been hitherto made ; and that these changes followed in all cases 

 the same laws, the representative curves being similar to one an- 



