765 



on the oscillations of the atmospheie. Those 

 oscillations appear to be owing to the sun, 



123, 274 5 Conn, des temps pour 1825, p. 312. The influ- 

 ence of the lunar attraction would be more easily ascertained 

 between the tropics, when the accidental perturbations mask 

 so little the play of the horary variations. I watched seve- 

 ral nights, without observing any thing satisfactory on this 

 subject ; but M. Mutis assures me he discovered that e< at 

 8auta Fe de Bogota the barometer mounts and descends 

 most in the quadratures, While at the epocha of the oppo- 

 sitions and conjunctions, the difference of ll h at night and 

 3j h in the morning becomes extremely small." M. Caldas 

 (Semanario, Vol. i, p. 55) mentions also this observation of 

 his master. It were to be wished that the meteorological 

 journals which M. Mutis kept duriug thirty to forty years, 

 were carefully examined, if several of those precious manu- 

 scripts were not dispersed after his death, during the 

 political troubles of New Grenada. M. Boussingault, who 

 devotes himself with the same ardour to the examination of 

 every physical phenomenon, has again gone over the labours 

 of M. Mutis (employing much more perfect instruments) in 

 the syzygies as well as the quadratures, at the hours of the 

 passage of the moon over the meridian, but he could not ascer- 

 tain the lunar influence on the barometric heights. He writes 

 to me from Santa Fe de Bogota, (February 9th, 1825), « I 

 dare not altogether deny," he writes, " the lunar influence 

 on the mean height of the mercury, but I believe that if that 

 influence exists, it is scarcely sensible, because it is lost 

 among the other causes of the horary variations." Seeking 

 to collect in this wdrk whatever can throw light on the Me- 

 Horology of the torrid zone, I believe it will be agreeable to 

 naturalists to find at the end of this memoir, a part of 

 M. Boussingault's observations on lunar influence. It will 

 be seen that the mean of the syzygies differs only 0.16 mm 



