328 METEOROLOGY AND ALLIED SUBJECTS. 



in the Indo Malayan, region as it is now first presented to us, is snch 

 that in those regions, where the effect of the sun is most direct, the 

 lowest atmospheric pressure coincides with the maximum of sun-spots. 

 {Z. 0. G. ill., XV, p. 394.) 



Hildebrandson has called attention to a valuable collection of data 

 on the variability of climate published by Ehrenheim in 1823, wliich 

 gives the years of severe winters for the past twelve hundred years, 

 and adds considerable to the data already collected by Koppen. [Z. 0. 

 G. 71/., XV, p. 345.) 



(b) Hi/psometry. — The new hypsometric formula of Dr. Guido Grassi 

 and its application to the reduction of barometric observations to sea 

 level, or to the barometric computation of altitudes, forms a memoir 

 published by the meteorological office at Rome. 



Professor Grassi has studied those formulae in which the temperature 

 being observed at one station some hypothesis is uecessarj^ in order to 

 approximate to the mean temperature of the column of air, and con- 

 cludes that the unsatisfactory results given by the formulae are due to 

 errors in the hypothesis on which they are based. His new formula, 

 which contains not onl}" the temperature and pressure of the upper 

 station, but also the moisture for both upper and lower stations, reads as 

 follows : 



"1 — I W. & + ! 



in which a represents the desired height above the sea, h the baromet- 

 ric pressure at the station, &othe barometric pressure at sea level, t the 

 absolute temperature at the upper station, C the correction for gravity, 



^•=58.6588, m=^ ( j^ + j Wherein /o and / are the force of vapor in 



millimeters at the u]iper station and sea levels, and/o can be computed 

 by Hann's formula : 



For reductions to sea level, Grassi transforms this formula iu the fol- 

 lowing : 



^"= ^^ +-w{ i-8»05 ^ + -u"K.^-s'^' ) h^ r 



The comparison between this formula and those given Euhlmann 

 and Saint-Robert shows that Ruhlmann's gives results nearer the truth 

 if we deal with annual means ; but Grassi's formula shows somewhat 

 less of the annual periodicity. [Z. 0. G. M., XIV, 1879, p. 31.) 



Dr. Jordan has deduced an empirical and new barometric formula 

 for use with a barometer established at some intermediate station. lie 

 first represents the temperature for an extensive net- work of stations 

 by a formula in which altitude and latitude occur as linear functions, 

 and from which the average rate of diminution of temperature with 



