£. Loomis—Reduction of Barometric Observations. 91 
Table III shows the results deduced from these observations 
in the manner already fully explained, the pressures being 
expressed in English inches, and the temperatures in degrees of 
Fahrenheit. These results do not differ very widely from 
those found for Grand St. Bernard, but the discrepancies 
between theory and observation are somewhat greater. The 
first question then is can these discrepancies be explained by 
the error in the assumed temperature of the air column? In 
order to answer this question I have sought for observations of 
the thermometer at stations intermediate between Colle di Val- 
dobbia and Alessandria and have found two, viz: Biella, 
elevated 434 meters above the sea, and Cogne, elevated 1543 
meters. The following table shows the mean temperatures of 
the four stations for each month of the year, deduced from the 
three years 1879-81. The sixth column shows the difference 
between the mean temperature of the air column and the half 
sum of the temperatures of the upper and lower stations. The 
sign + indicates that the former exceeds the latter. 
Aless’a| Biella. | Cogne. | Valdo'a) Temp. 
|Aless’a,| Biella. | Cogne vn Beinn Sf | excess. 
2. | ° ° ° | ° ° ° ° ° o ° 
uy —2°53/—0°43)—6°80/— 8°63) + 0°58) July __| 24°13) 21°37) 16°47) 9°27/—O1 
Febr’y | 2°47) 3°50 —3°63| 6°50/+0°31}|Aug’st | 23°30) 20°50) 15°10 9°80, — 0°38 
March 37, 7°33] + 1°10] —2°%3|—0°17 Sept. -| 18°47 15°97] 10°30) 56°40 —0-4( 
April -| 12°07; 9°87) 3°37;—1°63|—0°36 ‘Oct. ars 12-00, 11°00} 4°83) 0°67)/—0°04 
vas Ree 37) 13°20) 7°27) + 1-40]—0-01]/ Nov... 6°23) 677)+0°57 2°83! + O10 
June__) 20°37! 17-70| 12°00| 5-10 +0°11)/Dee. ..|—0°03; 1°87|—4°27|—6°201 + 0°55 
_ This table shows that in winter the mean temperature of the 
air column is almost 1° Fah. greater than the half sum of the 
temperatures of the upper and lower stations, and in summer 
the former temperature is a little less than the latter; but this 
error will only explain about ten per cent of the discrepancy 
etween theory and observation shown in table IIL 
omewhat more than half of the barometric minima occur at 
the same hour (i. e. the same hour of observation) both at Colle 
di Valdobbia and Alessandria. On an average for the three 
years, the barometric minima occur at Valdobbia three quarters 
of an hour later than at Alessandria, and allowirig for difference 
of longitude, the actual retardation at Valdobbia is at least three 
hours. The barometric maxima occur at Valdobbia on an 
curves at the upper and lower stations; i. e. to the dissimilar oe 
movements of the upper and lower strata of the atmosphere. 
reewe 
