1837.] Dip and Intensity at Madras. 377 



With a view to compare theory with practice, we might now com- 

 pute the number of oscillations which No. 3 x ought to make at 

 Madras from the observed number in London ; thus, assuming the 

 Dip for London to be 69° lO 7 N. the formula becomes 



{ 3 + sec. '^69° 10') } * : { 3 + sec. 2 (6° 52' 30") j* : : 462,76*1 ' : T* 



performing the computation T = 344,87 differing to the amount 

 of 44,57 seconds from the observations. This difference between 

 theory and observation, is but one of many instances which have from 

 time to time occurred in tbe infant state of a science. Observation 

 has led us to a theory, and then again has shewn the incompleteness 

 of such theory. In the case of Magnetism, we have long since been 

 prepared to expect that local causes might considerably interfere with 

 its established laws; since one station (the island of Teneriffe) has 

 already exhibited some singular anomalies, both in respect to the Dip 

 and Intensity. Under these circumstances it is much to be wished 

 that observations could be multiplied in various parts of India, where- 

 by the law of variation from theory may be detected ; — and how is 

 this to be accomplished ? My answer is ready : — Let any gentleman 

 who is disposed to undertake a set of magnetic intensity experiments 

 signify his intentions ; and I shall have great pleasure in forwarding 

 to him, free of expense, a magnetised and compared needle, provided 

 that I am favored with a copy of the results. In anticipation that 

 there will be several gentlemen disposed to forward this inquiry, I am 

 now preparing several needles for use. All that is necessary is, that 

 the person applying for a needle should be in possession of a good.cloclc 

 or chronometer, and has the means of ascertaining its daily rate. 



Madras Observatory, 9th May, 1837. 



Note. — We shall be most happy to promote the author's views by 

 making a series of experiments with his needles in Calcutta, and then 

 distributing them to friends in the interior. Of the dip we have a 

 few records, (see Proc. As. Soc. for May.) Major B. Blake also 

 brought from England an adjusted intensity needle, but we have not 

 yet been favored with his observations. — Ed. 



VI. — The Legends of the Saurashtra group of Coins deciphered. By 

 James Pkinsep, Sec. As. Soc. 



Those who would deprecate the study of old coins as a useless and 

 uninteresting waste of time and ingenuity, — and there are such we fear 

 even among the readers of this journal, — frequently mistake the means 



