Dr Richardson on the Aurora Borealis. S48 



The opinions I have ventured to advance above, are at va- 

 riance with the conclusions drawn by Captains Parry and Fos, 

 ter, from their observations at Port Bo wen,- — those officers io^ 

 ferrinsr that the aurora does not influence the motion of the 

 needle : but the discrepancy may be perhaps explained by the 

 difference in activity and altitude of the aurora in the two places. 

 I have stated that the needle is most affected when the aurora is 

 very active, and displays the prismatic colours. Captains Parry 

 and Foster have informed me, that the aurora seen at Port 

 Bowen was generally at a low altitude, without much motion in 

 its parts, and never exhibiting the vivid prismatic colours, or the 

 rapid streams of light, which are so frequently recorded in our 

 registers, of its appearance at Fort Enterprise and Fort Frank- 

 lin. At both these places, we as often witnessed the corrusca- 

 tions crossing the zenith, as at any other altitude, and under 

 such' a variety of forms, and in such rapid motion, as to baifie 

 description. 



From the difference in the appearance and activity of the au- 

 rora at Port Bowen, and Forts Enterprise and Franklin, an in- 

 ference may be deduced that the parallel of Q6° N. is more fa* 

 vourable for observing this phenomenon, and its effect on the 

 needle, than a higher northern latitude. 



A Sketch of the Climate of the Mediterranean^ with Remarks on 

 its Medical Topography ; being the result of Five Years'' 

 Observation. By the late William Black, Esq. Surgeon, 

 Royal Navy; and communicated by Dr Black of Bolton 

 in Lancashire. 



_L HE great basin of the Mediterranean, from its lying between 

 countries differing so remarkably in their several localities and 

 productions, has its general climate impressed with a mixed cha- 

 racter, which it is as interesting to study, as it is important to 

 analyse. Though the average climate for twelve months may be 

 called equable, which is the character it has in England, yet 

 there is, perhaps, no similar extent of water and coast where 

 great climatorial vicissitudes are so plentifully produced by dif- 



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