64 Questions Jhr Solution relating to Meteorology, 



barometer. Officers of great skill, Captain Basil Hall, Captain 

 Parry, and Captain Gauttier, have determined by observations, 

 the errors to which navigators are exposed by following the 

 common rule. It was sufficient for them to measure, either 

 with the dip-sector of Wollaston, or with the ordinary instru- 

 ments furnished with an additional mirror, and that in the most 

 varied states of the atmosphere, the angular distance of one 

 point of the horizon from the point diametrically opposite. Ad- 

 mitting, as we may be nearly at all times allowed to do, that 

 the state of the air and of the sea are the same all around the 

 observer, the difference of the distance measured at 180'', is evi- 

 dently double the real depression of the horizon. The half of 

 difference, compared to the depression of the tables, gives, 

 therefore, the possible error of every angular observation of 

 height made at sea. 



The positive and negative errors observed by Captain Parry 

 in the northern regions, have all been comprised bet\^een + 59" 

 and — 33." In the Chinese and East Indian seas. Captain Hall 

 found the deviations greater ; from + 1' 91' to — 9! 58". Final- 

 ly, Captain Gauttier, in the Mediterranean and Black Seas, 

 gives a still greater length, from + 3' 35" to — V 49". If it be 

 recollected that the variation of a single minute in latitude near- 

 ly corresponds to a deviation of 2000 metres on the globe, every 

 one will acknowledge how deserving of attention is the investi- 

 gation which we have just mentioned. 



By examining with care all the observations of MM. Gaut- 

 tier, Basil Hall, and Parry, we come to the conclusion, that the 

 error of the calcuLx\ted depression is not positive, and that 

 this depression does not exceed that ohsei'ved^ except to the 

 amount that the temperature of the air is higher than the tem- 

 perature of the water. 



With regard to the negative errors, they present themselves 

 indiscriminately in all the comparative thermometrical states of 

 the sea and atmosphere, without the possibility of attributing 

 these anomalies to any apparent cause, and, in particular, to the 

 degree of the hygrometer. 



MISCELLANEOUS OBSERVATIONS. 



Rising of the Coast of Chili. — In the month of November 



