METEOROLOGY. 



493 



storms occurred in November and December ; 

 March had 14 per cent., and September only 3 

 per cent, of the number. 



The cyclonic phenomena of New England 

 have been studied by Prof. Winslow Upton, 

 with especial reference to the distribution of 

 precipitation in tbe separate storm movements ; 

 a term of eighteen months, from January, 1885, 

 to August, 1886, with 41 storms, having been in- 

 cluded in the investigation. The storms were 

 classified into those approaching from the great 

 lakes on the west, 22 in number; those ap- 

 proaching from the south or southwest, 13 ; 

 and 6 special cyclones in which a secondary 

 development was formed on the Atlantic coast, 

 and two movements united. The author con- 

 cludes that, while the distribution of precipi- 

 tation in the several storms is very irregular, 

 and each storm seems to be well-nigh individ- 

 ual in this respect, indications of common feat- 

 ures are presented in them. The maximum 

 area of precipitation in the northern group of 

 cyclones which entered New England from the 

 west, lies south of their path at an average dis- 

 tance of about 100 miles; in the corresponding 

 southern group, it lies north of their path at an 

 average distance of about 150 miles; the maxi- 

 mum in those cyclones which moved north of 

 New England lies about 300 miles south of 

 their path, in central Massachusetts; in those 

 which entered from the south, it lies approxi- 

 mately along their path. Maximum areas of 

 precipitation in cyclones which have a second- 

 ary development, or in combined cyclones, are 

 found near the origin of the secondary develop- 

 ment, along the path of each of the component 

 cyclones and near the place of union. The 

 amount of precipitation is greater in storms 

 coming in from the south than from the west, 

 in the proportion of four to three. In double 

 cyclones, it is greater in that component which 

 comes from the south, which, in cyclones hav- 

 ing a secondary development is, in the cases 

 examined, the secondary cyclone. The great- 

 er amount of precipitation precedes the pas- 

 sage of the cyclonic centers. Finally, the direc- 

 tion in which the rain front and rear advance 

 is not always the same as that of the center of 

 the cyclone. The behavior of the cyclones en- 

 tering from the west possibly indicates a topo- 

 graphical peculiarity on account of which these 

 storms deposit a greater amount of rain or snow 

 in southern Vermont and New Hampshire and 

 southwestern Maine. 



The winds, at altitudes reached by high 

 mountains, are, according to the studies of 

 Mr. William M. Davis, of higher average ve- 

 locity than those of lower altitude, not only 

 on account of the absence of friction with the 

 ground, but also by reason of the greater steep- 

 ness of the basic gradients in the upper air, or, 

 in other words, the greater inequality of press- 

 ure in a given high-level distance. We may 

 be confident, also, that the winds on the high- 

 er mountain-tops are steadier than the lower 

 winds, in both velocity and direction. Tho 



winds of the upper levels are prevailingly from 

 some western quarter, even in those latitudes 

 where the surface currents flow from the east, 

 except very close to the equator. The absence 

 at high levels of both the "polar" and "equa- 

 torial" currents of the older meteorologists is 

 as significant as the gradual vertical extinction 

 of the lower cyclonic storm-circulation of more 

 recent authors. The general planetary circu- 

 lation of the winds, resulting from differences 

 of temperature between the equator and the 

 poles, is so far controlled by forces arising from 

 the earth's rotation that the general direction 

 is turned along parallels of latitude rather than 

 meridians. Although the average velocity of 

 the wind increases as we ascend, it is not un- 

 usual to find high-mountain winds for a time 

 exceeded by those passing over an exposed sea- 

 coast station during periods of storms. A spe- 

 cial characteristic of the upper winds is found 

 in the occurrence of their maximum velocity 

 at night instead of in the afternoon, as at the 

 earth's surface. The hills and mountains of 

 New England offer good ground for the study 

 of these diurnal changes. Veerings in direction 

 also take place, corresponding with the changes 

 in velocity. The morning retarded winds in- 

 cline to the left as their velocity decreases, and 

 the afternoon accelerated winds to the right, 

 as their velocity increases. On lowlands, the 

 change of direction will be reversed. Mount- 

 ainous regions are often characterized by winds 

 blowing down the valleys at night, and up the 

 valleys in the daytime, thus forming a local 

 current of diurnal period, commonly known as 

 mountain and valley winds. When the mount- 

 ain-sides are snow-covered, the upcoast wind 

 of the day is reversed into a cold, descending 

 wind. As a consequence of the normal valley 

 and mountain winds, mountain-peaks become 

 covered about noon, and in the afternoon may 

 receive rain condensed from the expanding, as- 

 cending current. At night, the cold air col- 

 lecting in the valleys, often produces lakes of 

 mist there, that melt away under the morning 

 sun. The air on the mountains is clearest and 

 driest during the latter half of the night. 



The common weather-cock, or wind-vane, is 

 one of the oldest as well as simplest of mete- 

 orological instruments. The fanciful forms 

 which it has assumed in popular use have been 

 replaced, in the application to accurate meteor- 

 ological observations, by simple plane plates, 

 disks, or arrows, designed solely with regard 

 to the mechanical action of the wind upon 

 them. The form in general use at present is 

 that of an arrow with a double or spread tail. 

 This spread form, when first introduced, con- 

 sisted of two thin plates joined at one end at an 

 angle of about 45. Its principle has grown in 

 favor, but the angle of the wings has gradually 

 been reduced to about 22J, and even less. In 

 practice the surfaces are made with a slight 

 curvature, so that the actual angle made by 

 their tangents increases from zero at the ver- 

 tex to 30 or more at their extremities. George 



