72 VOYAGE TO THE 



but these winds, though they blew direetly upon the 

 coast, were generally attended by clear weather, which 

 would have enabled a vessel to find a port, had it been 

 necessary. They were strongest about the full and 

 change of the moon. 



From the prevalence of the westerly swell oft' the 

 harbour, and from the wind moderating as we ap- 

 proached the coast in both years, I am inclined to 

 think that these winds do not usually blow home 

 upon the shore. 



There was a curious anomaly observed in the 

 movements of the barometer and sympeisometer 

 during our stay at San Francisco : the former rose 

 with the winds which brought bad weather, and fell 

 with those which restored serenity to the sky. The 

 maximum height was 30-46, the minimum 29-98, and 

 the mean 30-209. 



The hygrometer on the whole indicated a dry 

 atmosphere, and ranged from 0° to 20' of dryness on 

 the thermometric scale, the mean degree of dryness 

 being 6 ', 6'. The particulars of these observations are 

 inserted in tables in the Appendix to the 4to edition. 



The clear weather occasioned by the north-west 

 wind was favourable for astronomical observations ; 

 but many were lost in consequence of a haze over- 

 hanging the land at night, and from the incovenience 

 arising from a heavy deposition, which, besides occa- 

 sioning much mirage, fell so profusely upon the 

 glasses of the instruments that they were obliged to 

 be repeatedly wiped, and sometimes at the most in- 

 convenient moments.* Our observations, however, 

 were very satisfactory, and are important, as the 



* I found this in a great degree obviated by fixing a long paper 

 tube to the field end of the telescope. 



