180 METEOROLOGY. 



the course of the loiver clouds, under the head of "winds." The 

 motion of these lower clouds may justly be said to indicate the real 

 course of the wind ; for in such a mountainous country as this the 

 atmosphere at the bottom of the kettle-shaped valley of the colony, 

 is set in motion by a great number of local causes, and this motion 

 is changed and modified by the many ravines and watercourses, and 

 by every slope of the irregularly shaped mountains. The colony is 

 surrounded by mountain ridges, crowned by several peaks. These 

 barriers open only in one direction, towards the east, where they form 

 an outlet for the river Tuy, which has its sources in the neighboring 

 fields and adjacent forests. In such a region as this it is next to im- 

 possible to note, even in one narrow district, all the diiferent little 

 breaths and jerks of wind, which frequently change every moment. 



As to the motion ot the lower clouds, they frequently showed a 

 velocity which I estimated at about 7 miles per hour ; and as there is 

 no number corresponding to this velocity in the tables, I introduced 

 the number " 2^," which means 7 miles per hour. 



Fog is a considerable item in this region in the rainy season, and I 

 have accordingly noted it down under the head of " kinds of clouds." 

 Thunder and lightning are very rare here, and when they occur 

 they make so little show that, with regard to force, they may be com- 

 pared to those of the United States as the zephyr to a strong gale. 

 In the register I have noted them down in the margin. 



Tornadoes I have never seen in thecolony_, not even a gale of wind, 

 within the two and a half years that I have been living here. Hail 

 storms are unknown in this part of the country. 



Of the 48 observations recorded in July, at 7 a. m. and 2 p. m., on 

 the course of the lower clouds, 10 are E., 15 E.SE., and 15 8E., which 

 shows the prevailing winds to be between E. and SE. Their mean 

 velocity is a fraction over four miles per hour. 



Of rain, fog, mist, and clouds, we had more than a sufficiency, the 

 mean cloudiness being 6.4. 



The weather has been so unfavorable since my return from the 

 States that I have not yet measured any of the neighboring heights 

 and passes by barometer. 



The thermometer in the open air shows a mean temperature of 58.3 

 for the month of July, a rather low temperature for the height of 

 6,500 feet in latitude 10° 26'. The minimum of the month was 54°, 

 the maximum 69°. 



I also inclose the half-hourly and hourly barometrical observations 

 for seven days, made in order to ascertain the hour of maximum and 

 minimum of the daily periodical variations. And here I found that 

 these variations within the tropics, at least at the colony, are not so 

 regular as we sometimes find stated in books. As, for instance, the 

 following: "Such is the regularity with which these motions are 

 efiected within the equatorial zones that they might there serve to 

 give the true time of the day." — (Nicollet, Essay on Meteor. Observ., 

 page 7.) Eor we find maximums at 9^ a. m., 10, 11, 12 m., and 

 minimums at 4 p. m., 4^, 5, 5^, 6^ 6|, 7, and all this within the short 

 period of seven days. This irregularity is the more remarkable, as the 

 colony is a place where none of the extremes of heat and cold, or of 



