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 XXXIX. Intelligence mid Miscellaneous Articles. 



SUGGESTIONS FOR THE OBSERVATION OF THE ANNULAR 

 ECLIPSE, OCT. 9, 1847, MADE BY THE BRITISH ASSOCIATION 

 FOR THE ADVANCEMENT OF SCIENCE, OXFORD, JUNE 2(), 



1847. 



n[ "^HE following directions and suggestions, relative to the ensuing 

 -■- annular eclipse of the sun, which will take place Oct. 9, 1 847, are 

 proposed for the assistance of less-practised observers, or those who 

 may not have better information at hand, but who may nevertheless 

 render great service by noticing and recording, as well as circum- 

 stances permit, any of the various points herein alluded to. 



I. As a general direction as to the limits within which the eclipse 

 can be seen annular in England and Ireland, if on any map a line be 

 drawn through Greenwich and Gloucester and produced, it will give 

 the northern limit at which the eclipse ceases to be annular. 



A line parallel to the last, through Padstow in Cornwall on the 

 west, and Torbay on the east (which will extend across the channel 

 to Havre, &c., and passes just below Cape Clear on the west), will 

 be the line along which the eclipse is both annular and central. 



The southern limit lies wholly below England. 



II. As a rough guide to the time, the commencement of the an- 

 nulus will be nearly at 7** 23™ a.m. (civil reckoning) for the extreme 

 south-west of Ireland, at 7** 24"^ for a line through Land's End and 

 Milford Haven, at 7^* 2.5"" through the Isle of Wight and Reading, 

 at 7^* 25"" 50^ forWalmer (Greenwich mean time). 



III. For the observations requisite, a telescope of very moderate 

 power is best. As the annulus will not last more than three or four 

 minutes, those unaccustomed to such observations should be cau^ 

 tioned against attempting to observe all the phsenomena, or they 

 may thus run the risk of observing «OMe. If possible several observers 

 should combine for the purpose, and each agree to attend to one, or 

 some few of the phsenomena. 



IV. To obviate some of the difficulties arising from the rapid 

 passage of the phsenomenon, the observer may be referred to Capt. 

 Smyth's Cycle (i. 141, 146), where some valuable practical hints 

 are thrown out for tranquillizing the observer's nerves in so transitory 

 a phsenomenon ; especially by previously making a careful drawing 

 of the spots (if any) existing on the sun's disc, which may be made 

 useful in marking and ascertaining the progress of the ecHpse. 



V. With the view of correcting the moon's tabular north polar 

 distance and semidiameter, it is peculiarly desirable that observations 

 should be made along or near the line (passing through Greenwich 

 and Gloucester) on which the eclipse is barely annular. At some 

 of these the echpse will be completely annular, and here the follow- 

 ing observations should be made : — 



The time of beginning of annularity and end of annularity should 

 be observed. As the duration only is required, a common watch 

 showing seconds will suffice for this purpose. 



