£. Loomis—Reduction of Barometric Observations. 85 
cipal fluctuations, but the minor fluctuations at the two stations 
thirds of that at Summit. The curve for San Francisco accords 
better with that at Summit than does the curve at Sacramento, 
and the range of the barometer is greater: For the month o 
April, 1873, there is not a single point of resemblance between 
the curves at Sacramento and Summit, and the entire range of 
the barometer at Sacramento 1s only 54 per cent of that at 
Summit At San Francisco, on the contrary, in the large fluct- 
uations, the barometric curve shows considerable resemblance 
to that at Summit, and the range of the barometer is almost as 
great. These facts seem to furnish the clue to the anomalous 
character of the barometric observations at Sacramento. Sacra- 
mento is situated in a valley between two ranges of mountains. 
On the east are the Sierra Nevadas, 7000 feet in height, and 
on the southeast they rise to the height of 10,000 to 12,000 
feet. On the west side, is the Coast Range of mountains, rising 
to the height of 3,000 to 4,000 feet, with a gap about fifty | 
miles wide, through which flows the Sacramento river. From 
the summit of the Coast Range to the summit of the Sierra 
Nevadas, is but little more than 100 miles. Inu this valley of 
the Sacramento it is not possible that there should be much 
cyclonic motion o win The winds at Sacramento 
almost always blow up or down the valley, and the winds from 
the three directions W., E. and N.E. form only eight per cent of 
the entire number for the year. The marked resemblance 
between the curves at San Francisco and Summit for the larger 
barometric fluctuations, seems to indicate that the cyclonic 
motion of the winds at San Francisco is sometimes propagated 
obliquely upward to the summit of the Sierra Nevadas, and in 
such cases it sometimes leaves no sensible trace of its influence 
at Sacramento. This comparative freedom of the air at Sacra- 
ummit and Sacramento is 60449 and that of the temperature 
coefficient is . 
_4 next proceeded to make a similar comparison of observa- 
tions made at Grand St. Bernard and Geneva. As the Biblio- 
théque Universelle de Genave only gives the daily averages of — oe 
‘the observations for 1877-9 (the observations employed in my. 
fifteenth paper) I selected the years 1858, ’59 and ’60 for which a 
