July i i, 1895] 



NA TURE 



243 



)iis inability to give a diagnosis of the Picariii;, that is in 

 the logical sense, but claims that the group as selected 

 by him possess "certain common features not found 

 among the Passeres." In the last chapter in this \()lume, 

 he treats of the Jacamars to the Toucans. 



Coiirs Eh'mcniairc cf ElcLtricih'. By M. B. Brunhes. 



Pp. 265. (Paris : Gauthier-V'illars et Fils, 1895.) 

 Thk experimental laws and general principles belonging 

 to the study of teclinical electricity are set forth in this 

 liook in an elementary, but strictly scientific, manner. 

 The book reproduces the author's tirst-year course of 

 theoretical electricity at the Institut industriel du Nord 

 dc la France, and its contents furnish just the kind of 

 foundation needed by students of electrical engineering. 

 In several respects, the treatment difters from that gene- 

 rally followed in text-books; hydrodynamic analogues 

 are entirely omitted, and the word potential is not em- 

 ployed, voltage, or E.M.F. between two points, being used 

 to express potential difference. 



Off the Mill : Soiin' Ocoisional Piipcrs. By (1. F. Browne, 

 B.I)., U.C.L., Bishop of Stepney. Pp.271. (London: 

 Smith, Elder, and Co., 1895.) 



Al.l'lXF. climbers, and others who find delight in motni- 

 tain-peaks and glaciers, may like to read the papers on 

 y\lpine subjects reprinted in this volume. The papers 

 originally appeared thirty years ago, and they offer to 

 the present generation of mountaineers an interesting 

 picture of the way in which climbs were then made. 

 The ice-caves in the neighbourhood of Annecy form 

 the subject of one of the papers appealing to scientific 

 read<rs. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondetits. Neither can he nnderlake 

 to return, or to correspond with the writers of, rejetled 

 manuscripts intended for this or any other part of NATURE. 

 No notice is taken of anonymous communications. ] 



A Cyclonic Indraught at the Top of an Anticyclone. 



liK'IW'KKN June 7 and 12 an anticycltine, with maximum 

 pressure of 30*20 to 30'30 inches, passed slowly from the north- 

 west acr<tss southern New England. The isoljars formed well- 

 defined ovals, with their longer axes running from south-west to 

 north-cast. It was difficult to locale the centre of the anti- 

 cyclone because the isobars were broken on the side toward the 

 ocean ; l)iu. by drawing a line llirough the stations showing the 

 maximum pressure, the crest or ridge of the anticyclone could 

 be easily located up to the Ilth, after which it passed otT the 

 coast and its position became somewhat uncertain, although the 

 pressure continued above normal over southern New England 

 until the night of the I2lh. 



The interest attaching to the anticyclone lies in the fact that 

 cirrus observations obtained on botli sides of the line of maxi- 

 mum pressure indicate an indraught at the lop of the anticyclone 

 of the same nature as that observed at the bottom of cyclones. 



The anticyclone passed nearly centrally over the Klue Hill 

 Meteorological Observatory. As it approached from the north- 

 west, the cirrus clouds on the 8th were observed moving from the 

 south-southeast. As the line of maximum pressure jxissed over 

 the observatory on the gth, the cirrus movement shifted to the 

 north-c.ast, frcmi which direction it was observed on the lolh and 

 nth. This change corresponds almost exactly with what would 

 be observed in the surface wind should a trough of low 

 pressure pass over Blue Hill from the same direction. On the 

 12th the cirrus shifted to south, and on the 13th to the west, 

 with the a]iproach of a cyclone from that direction. 



The direction of cirrus movement and the mean direction of 

 the wind is recorded at the observatory in degrees of a/imuth 

 beginning with the south point. The first is measured with a 

 nephoscope, and the seciind recordetl by a Draper anemoscojie. 

 The following table gives the cirrus and corresponding wind 

 observations between the 8lh and loth, no cirrus observations 



NO. I34I, VOL. 52] 



being obtained on the 7th. The velocities of the cirrus were 

 obtained by multiplying the observed relative velocities by a 

 factor to reduce to absolute velocities. This factor was deter- 

 mined from direct measurements of cloud heights and velocities 

 carried on for some time at this observatorj'. The last column 

 in the table contains the directions in degrees of azimuth of the 

 line of maximum pressure in the anticyclone, taken from the 

 maps of the United States Weather Bureau. 



Cirrus. Wind. 



The changes in the direction of the cirrus and of the surface 

 wind, as related to the line of maximum pressure, is shown 

 graphically in the accom)ianying diagram. The line nf maximum 



Cirrus 



Wind. 



MILES 

 100 200 



pressure is indicated in each case by the long slanting line. The 

 arrows Hy with the cirrus and with the wind, and the length of 

 the arrows indicate the velocity, though on a different scale in the 

 two cases. The small figures near the arrows give the dates of 

 observation. 



Repeated observations of this kind, here and elsewhere, ought 

 to throw some light on the causes of cyclones and anticyclones. 

 If an indraught prevails at the top of the anticyclone of the same 

 nature as the indraught at the earth's .surface in a cyclone, it 

 seems difficult to avoid the conclusion that there is an area of 

 low pressure in the upper air above anticyclones, notwithstanding 

 the fact that studies of mountain observations by Hann and 

 others lead to an opposite conclusion. In the present case the 

 inward gradient above appears not to have extended entirely to 

 the outer limit of the anticyclone .as indicated by the observations 

 (m the I2tb. 



Direct observations of the anticyclonic inflow must, however, 

 be rare : first, because of the infreipiency of cirrus in the proper 

 positions, and the general absence of exact methods of measuring 

 the slow motions observed ; second, because there is usually a 

 strong eastward drift in the upper air, which greatly interferes 

 with the anticyclonic circulation, and generally overrides it, 

 so that it only becomes strongly marked under stagnant con- 

 ditions of the general atmosphere ; third, the upper air isobars 

 are usually distorled by strong contra.sts of temperature in the 

 area of the anticyclone. But notwithstanding these drawliacks, 

 I am confident that with the increasing attention given to 

 cloud observations, cases like the present will be frequently 



