24 ADMIRALTY INSTRUCTIONS. 



" 7. In some of those singularly heavy showers 

 which occur in crossing the Equator, and also at 

 the changes of the Monsoon, attempts should be 

 made to measure the quantity of rain that falls in 

 a given time. A very rude instrument, if properly 

 placed, will answer this purpose, — merely a wide 

 superficial basin to receive the rain, and to deliver 

 it into a pipe, whose diameter, compared with that 

 of the mouth of the basin, will shew the number of 

 inches, &c. that have fallen on an exaggerated 

 scale. 



"8. It is unnecessary to call your attention to 

 the necessity of recording every circumstance con- 

 nected with that highly interesting phenomenon, 

 the Aurora Australis, such as the angular bearing 

 and elevation of the point of coruscation ; — the 

 bearing also of the principal luminous arches, &c. 



"9. It has been asserted that lunar and solar 

 halos are not always exactly circular, and a general 

 order might, therefore, be given to the officer of 

 the watch, to measure their vertical and horizontal 

 diameters whenever they occur, day or night. 



" Large collections of natural history cannot be 

 expected, nor any connected account of the struc- 

 ture or geological arrangements of the great islands 

 which you are to coast ; nor, indeed, would minute 

 inquiries on these subjects be at all consistent with 

 the true objects of the survey. But, to an observant 

 eye, some facts will unavoidably present themselves, 

 which will be well worth recording, and the medical 



