164 METEOROLOGICAL OBSERVATORIES. 



the authority on high-level observatories, and I can refer the fellows 

 with confidence to his many works, which will all be found in our 

 library. 



I must, however, show you one view of the Pikes Peak Mountain in 

 Colorado, and I do this partly because in it Mr. Cohen has caught a 

 very happy effect of cloud. The mountain is over 14,000 feet in height, 

 and although on the south side it is approached by a gentle slope, yet 

 on a nearer view from the east or west sides would be found to be inter- 

 sected by deep gorges with precipitous walls 2,000 feet in height. On 

 the observatory which surmounts Pikes Peak a wind velocity of 92 miles 

 an hour was registered in December, 1892. 



I also show you views of the observatory on the Brocken Mountain, 

 and that of the Deutsche Seewarte at Hamburg, which latter enjoys 

 the distinction of being the largest meteorological observatory in the 

 world. 



EIFFEL TOWER, PARIS. 



From mountains to towers is a long step downwards, and I must ask 

 you for a moment to listen to a few particulars about the observations 

 taken on the Eiffel Tower in Paris, of which I show you a photograph, 

 and I should have been glad to give you a nearer view of the meteoro- 

 logical appliances on the top, but, up to the present, it has been found 

 impossible to get a satisfactory photograph of them on account of their 

 elevated position. 



On the top of the Eiffel Tower is a self-registering barometer, while 

 in the Bureau Central Meteorologique in the rue de l'tlniversite, there 

 is another, its exact counterpart, and it has been noticed that the first 

 diurnal minimum of air i^ressure at 4 to 5 in the morning is much more 

 evident at the top of the tower than at the base, while the first maxi- 

 mum at 9 or 10 in the morning is a good deal less marked on the sum- 

 mit than below. The second minimum of 14 h (2 to 5 in the afternoon) 

 is also less on the summit; the second maximum at 22'' (10 in the even- 

 ing) is sometimes a little more pronounced at the summit, but the dif- 

 ference is slight. The general corrected average pressure throughout 

 the year at the top of the tower is lower by 0.12 millimeter, about four 

 one thousandths of an inch, a difference not yet satisfactorily explained. 



As to temperature, it is generally from 1° to 4° C. colder on the 

 tower than below, the month of December being the only one where 

 the temperature is higher at the summit than at the base. The changes 

 of temperature are less regular, the diurnal variations not so large, 

 while the smaller oscillations are much more marked at the summit than 

 at the base, it often happening that some are registered above which 

 are absolutely inappreciable below. Some of the changes of tempera- 

 ture recorded in the tower are very remarkable, as for instance a leap 

 upward of 10° C. (18° F.), which rise of temperature took two days to 

 communicate itself to the stratum of air below. 



AH this and much more of great interest to the weather student may 



