288 METEOROLOGY AND ALLIED SUBJECTS. 



eons conclusions may be deduced from such sbort periods. By ex- 

 pressing the annual rainfall for each station as a percentage of the 

 average of a long series, Haun studies the simultaneous distribution ©f 

 relative rainfalls and the probability of wet or dry years. {Z. 0. G. If., 

 XVI, p. 339.) 



Wojeikof has collated the records of heights of water recorded on 

 gauges in American fresh-water lakes, the Great Bait Lake, the Sea of 

 Ladoga, the Caspian Sea, &c. He finds that in all cases the epoch of 

 maximum water was in the beginning of the decennium 1860-1870, but 

 the minimum of 1872-73, is not so uniform ; the Caspian Sea he denom- 

 inates the greatest rain gauge and evaporimeter of the globe. {Z. 0. 

 G. 3L, XVI, 1881, p. 288.) 



Max Moller, of Flensburg, communicates the results of careful obser- 

 vations of the cirrus-clouds. He finds that when a barometric minimum 

 is moving from west to east, the well developed cirri on the eastern edge 

 of the cloud-bank have a principal striation from west to east and a 

 combing-out — namely, a cross-striation toward the north j while in the 

 rear of the cloud-bank with a clearing sky the principal striation runs 

 from north to south and the comb-teeth point to the east. Such de- 

 pressions throw out towards the west only a plume of cirri whose north- 

 ern edge is bounded by a region of high barometric pressure, and in 

 such cases the area of low pressure shows only a slight tendency tx) 

 change of location. The absolute motion of the cirri is directed by the 

 upper winds there prevailing, the striation on the other hand is con- 

 trolled by the motion of the various strata of air relative to each other. 

 The variable angle between the direction of the upper wind and the 

 striae of the cirri will probably give some conclusions as to the course 

 of the isobars in the upper strata of air. {Z. 0. G. M., XVI, 1881, p. 246.) 



Professor Winkelmann has attempted a solution of the question how 

 large a geographical district should be included in a given special pre- 

 diction as to the occurrence of rain. He considers the question from a 

 purely statistical view, and proposes to determine for any given region 

 how often rain occurs at one station without occurring generally af all 

 stations, and how far we may go from one station without coming to 

 those whose rainy weather does generally not occur simultaneously with 

 that at the starting point. On applying his formulae and methods to 

 ten years of record at ten stations in Wurtemberg, he finds that on the 

 average for any one of these stations the weather is the same as that pre- 

 vailing at the other stations on eighty-five days out of one hundred, the 

 extreme values being .87 in 1871 and .82 in 1867. Thus one prediction 

 for the whole re^on will, on the average, sufilce to secure 85 per cent, 

 of verifications ; the division into two smaller districts will raise this 

 percentage to 87 per cent. {Z. 0. G. M., XVI, 1881, p. 236.) 



Blanford has published the meteorological observations made by Dr. 

 J. Scully in Western Thibet, in 1876, during "Shaw's Mission." These 

 observations afford an excellent check upon the applicability of Haun's 



