758 



greater number of observations of equal preci- 

 sion are made for the different zones. Provi- 

 sionally, we may adopt as the type most gene- 

 rally recognized of maxima and minima ; in the 

 equatorial zone: + 21i h ; — 16 h ; + 10J h ; 

 — 16 h . In the temperate zone: + 2G! h ; — 3i h ; 

 + 9i h ; — 14\ astronomical time, reckoned from 

 noon. 



2°. In the temperate zone the epochas of the 

 maximum in the morning and the minimum of 

 the evening, are one or two hours nearer the 

 passage of the sun over the meridian in winter 

 than in summer; but the type of summer is 

 that which most resembles the type observed 

 between the tropics. Observations are wanting 

 above all, for the minimum which takes place 

 after midnight ; it were to be wished that the 

 influence of the variable epocha of sunrise, on 

 the hour of the morning minimum, could be ex- 

 amined. 



3°. In the torrid zone, the limit-hours (that 

 is, the instants when the oscillations attain the 

 maximum and the minimum), are the same at 

 the level of th€ sea, and on table-lands at the 

 elevation of from 1300 to 1400 toises. It is as- 

 serted that this isochronism is not manifested 

 in some parts of the temperate zone, and that 

 *at the convent of the Great Saint Bernard, for 

 instance, the barometer lowers at the same 

 hours when it rises at Geneva. If this pheno- 



