150 



NA TURE 



[June i8, 189- 



and since that time he has organized no fewer than three 

 important expeditions, in the third of which he succeeded 

 in reaching the top of Kihmanjaro. It is this third 

 expedition of which an account is given in the 

 present work. The broad results of the journey 

 were soon made known ; but of course it is only from the 

 explorer's full narrative that an adequate idea can be 

 formed of the interest and importance of his achieve- 

 ments. The mountain mass of Kilimanjaro towers up to 

 a height of nearly 20,000 feet, and Dr. Meyer describes 

 well the feelings with which he saw it after his arduous 

 march across the steppes. " It was a picture," he says, 

 " full of contrasts— here the swelling heat of the equator, 

 the naked negro, and the palm-trees of Taveta— yonder, 

 arctic snow and ice, and an atmosphere of god-like re- 

 pose, where once was the angry turmoil of a fiery volcano.' 

 The story of the ascent is told most vividly, and there are 

 few readers who will not sympathize with the delight 

 with which he speaks of the moment when he set foot on 

 the culminating peak. Although the record of his ex- 

 periences at Kilimanjaro forms the centre of the book, he 

 has much to say about what he saw both on his way to 

 the mountain and on his way back ; and in appendices 

 various writers present classifications of his collections, 

 and the conclusions at which they have arrived in work- 

 ing out his astronomical and meteorological data. The 

 book is admirably translated, and its value is greatly 

 increased by illustrations and maps. 



Chemistry in Space. From Prof. T. H. van 't Hofif's "Dix 

 Annees dans I'Histoire d'une Theorie." Translated 

 and Edited by J. E. Marsh, B.A. (Oxford : Claren- 

 don Press, 1 891.) 

 We have already reviewed the monograph of which this 

 Is a translation (Nature, vol. xxxvii. p. 121), and need 

 not therefore, at present, say anything of the subject with 

 which it deals. The translator has done his work care- 

 fully, and " the invaluable assistance and advice " of the 

 author have enabled him to make his rendering " a con- 

 siderable extension of the French edition." Mr. Marsh 

 advises those to whom the question is new to leave the 

 first chapter till the end, as it contains a translation of 

 the earliest memoirs on the subject, and the ideas are in- 

 completely developed, obscure, and sometimes erroneous. 



LETTERS TO THE EDITOR. 



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

 pressed by his correspondents. Neither can he undertake 

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

 manuscripts intended for this or any other part of "^ KTM'SJL. 

 No notice is taken of anonymous communications. "l 



Erratic Track of a Barometric Depression, 



The singular course of the cyclonic system which has, during 

 the week terminating on May 29, circulated round and across 

 the British Isles, deserves more attention than can be thus 

 early given to it. I wish here, with your permission, first, to 

 describe the path of its centre as correctly as can be done with 

 the data at present in my hands, mentioning at the same time 

 the principal modifications of the isobars and of the weather in 

 the neighbourhood of the centre ; secondly, to mention some 

 remarkable facts in relation to the upper currents as observed 

 by myself in its neighbourhood ; and finally, to indicate the 

 nature of those questions an examination of which will, I 

 believe, in the instance before me, prove to be of most scientific 

 value, 



(i) The accompanying chart shows the course of the centre 

 of depression, so far as we have yet been able to follow its 

 track, the arrow-heads marking the position at 6 p.m. of each 

 day. At 8 a.m. of the 23rd, the centre appears to have 

 lain about 60 miles to the west of Erris Head, with a baro- 

 metrical pressure of a little below 29 '4. By 6 p.m. it had 

 advanced south-eastwards into Connaught with a velocity of 6 '5 



NO. I I 29, VOL. 44] 



English miles per hour, and by 8 a.m. of the 24th to a Ihtle west 

 of St. Anne's Head. During the above period the depression was 

 elongating itself, the position of its major axis changing from 

 N.W.-S.E. into W.-E. The weather in the meantime was 

 becoming rainy in the English Channel and home counties, 

 while continuing fair in the north. At 6 p.m. of the 24th the 

 eastward elongation of the whole system had become very 

 marked ; and at this hour the centre lay over the mouth of the 

 Thames, after a somewhat lengthened thunder-storm over 

 London, Woolwich, &c. The velocity of transit during the 

 twenty-four hours had been 22 miles per hour, and the path of 

 the centre was beginning to curve towards the left. By the 

 morning of the 2Sth the centre had advanced to N.N.E., and 

 lay about 53° 2' N, lat., 0° 24' W. long., with wet and cloudy 

 weather over our eastern and midland districts. By 6 p.m. of 

 that day the centre had begun to move slightly to the west- 

 ward, having moved during the twenty-four hours with a velocity 

 of 10 miles per hour. By the morning of the 26th the centre 

 was near the mouth of the Humber, rainfall continuing over the 

 north-east and north midland counties; at 6p.m. of that day 

 the centre lay over north-west Lincoln, having moved only with 

 a velocity of about 3-8 m. per hour. The centre now moved to the 

 neighbourhood of the Solway, with a velocity of about 10 miles 

 per hour, and on the evening of the 27lh began to recurve again 

 a little to the left, the system at the same time becoming more 

 circular in form, and the central pressures slightly decreasing. 

 During this day rain and cloud prevailed on the west of the 

 system, while in its rear there were some scattered thunder and hail 



showers of the type prevalent in summer in the rear of cyclonic 

 systems travelling to north-east. At 6 p. m, on the following 

 day the central area had passed into Ulster, with a velocity of 

 5 '5 miles per hour. The thunderstorms in the rear were on that 

 day u:ore pronounced. During the following night the centre 

 travelled with increased velocity across Donegal to the Atlantic, 

 and by 6 p.m. of the 29th the exterior isobars of the system had 

 almost left our shores, finer weather setting in over Great 

 Britain generally, 



(2) The point marked with an asterisk on the chart marks 

 the position of the writer during the progress of the depression, 

 a position of vantage for the observation of upper currents, the 

 value of which was much diminished by the predominant thick- 

 ness of low cloud, and by the fact that there was little moonlight. 

 Over the Midlands outlying threads of " cirro-filum " advanced 

 with great velocity from north-north-west at noon of the 23rd, 

 soon after which a great sheet of frozen veil-cloud rapidly 

 overspread the sky, the exterior edge of which soon disappeared 

 over the north-east horizon. A brilliant solar halo was con.- 

 pletely eclipsed before 5 p.m. Meanwhile the lower cloud- 

 current backed from south-west to south. At 7.32 p.m. there 

 was a squall of wind from south-east with rain, and a "jump " in 

 the barograph. About noon of the following day, when the centre 

 was about 118 miles to the south-south-west a glimpse of the upper 

 clouds was obtained ; they were then moving from south. 

 Further opportunities of observation were obtained in the 



