186 METEOROLOGY. 



made by Dr. G. Englemann in 1851, which shows the remarkahly 

 small monthly variation in the colony against the extreme range of 

 atmospheric pressure at St. Louis. 



In all these illustrations the barometer height has not been reduced 

 to the freezing jJoint for want of the necessary tables ; but, as the 

 difference of temperature connected with these observations does not 

 range much over 8 degrees F., the results may be considered not far 

 from their true value. 



Table No. 5 shows that the most prevailing currents of air at an 

 elevation of about 7,000 or 8,000 feet above the level of the sea, in the 

 months of June, July, August, September and October, are here from 

 E., E.SE., SE., S.SE.,and S., but especially from SE. 



Table No. 6 contains half-hourly barometrical observations for 17 

 days, taken down at three different periods of the year. From this 

 and* from sheet No 1 we see that the amplitude of the daily periodical 

 variations is not a constant quantity in one and the same place, but 

 changes with the different periods of the year ; as also does the hour of 

 maximums and minimums. To find out, by continued observation, 

 the mean amount of amplitude and the precise time of the maximums 

 and minimums ibr each month of the year seemed to me desiderata of 

 much interest to meteorology. 



With a view to investigate this matter I have made observations 

 accordingly. The first set I made Irom 18th to 24th June; the 

 second, from 1st to 7th October ; the third, from 10th to 12th Novem- 

 ber, and the fourth, from 22d to 28th December. These observations 

 give the mean amplitude for the latter part of June 058 ; for the 

 first part of October, 0.079 ; for November, 0.060, and for the end of 

 December, 0.043. 



By a peculiar view of the cause of periodical variations, and by the 

 aid of an artificial globe, I had calculated as early as last September 

 that the amplitude at Colonia Tovar ought to be greatest about the 

 16th May and 26fch September, and least on the 21st January. The 

 above-mentioned numbers of amplitude for October, November, and 

 December coincide with my calculations so far, and it remains to be 

 seen how they will do for the remaining portion of the year. 



With regard to temperature I will only say that the mean of the 

 three months of June, July, and August, (that is, of the meteorological 

 summer,) is 58 9 ; the mean of September, October, and November 

 (the meteorological autumn) is 58.9, or exactly the same. The mean 

 temperature of December is 56.6. During 204 days (from June 10 

 to December 31) the sky was only once free of clouds at 2 p m., 18 

 times free at 7 a. m., and 41 times at 9 p. m. Of these 204 days 143 

 were rainy days. 



On the 5th of January I made a botanical excursion to one of the 

 highest mountains of this region, about twelve miles to the east of 

 the colony. The mountain, according to my estimation, may be about 

 7j800 feet above the level of the sea, and is a kind of central point or 

 knot, from which several rivers, flowing in different directions, take 

 their origin. This mountain is covered by a dense forest, with the 

 exception of a level spot of about half a mile in length and a quarter 



