458 



NA TURE 



[March 22, 1877 



as regards the errors of the instruments employed and the heights 

 above the sea, so far as known. The heights of places not yet 

 determined trigonometricallyare approximated to barometrically 

 by a comparison with other stations whose heights are known. 

 From these data the monthly and annual isobars for each milli- 

 metre (o"039 inch) are drawn on thirteen maps. It is to be 

 regretted that so much work, characterised not only by general 

 accuracy, but also by an attention to minute accuracy of detail 

 in certain directions, can only be regarded as to a great extent 

 thrown away, at least in so far as regards the inquiry in hand, 

 viz., the representation of the facts of atmospheric pressure in 

 Russia, as that pressure varies by latitude and season, in their 

 relation to configuration of surface and the relative distribution 

 of land and water. The author has failed to see that, in order 

 to give a satisfactory solution of this problem, one of the first 

 requisites is that the observations at the different stations be for 

 the same terms of years, or be reduced to the same terms of years, 

 by the process of differentiation. As regards the thirty Russian 

 stations, the averages are for periods varying from seven to fifty 

 years, and excepting Lugan and Catherinenburg, no two places 

 are for the same terms of years. As regards the months the 

 result of this method of discussion is great unsatisfactoriness. 

 Thus at several places where the averages are only for a few 

 years, they not unfrequently are very different from the 

 isobars which have been drawn for the districts where they 

 are situated. Still further, the anomalous directions of several 

 of the isobars, such as the isobar of 759 millimetres for March, 

 cannot be accounted for by the physical peculiarities of the re- 

 gion traversed by the anomalous portion of the curve ; but an 

 examination of the facts suggests that the anomaly is probably 

 due to the simple circumstance that exceptionally high or low 

 mon'hly means of particular years are included in the averages 

 of some stations, whilst at other neii^hbouring stations observa- 

 tions were not made during these exceptional months. The 

 annual isobars are necessarily more satisfactory. It may, how- 

 ever, be noted that if allowance be made for the correction for 

 gravity, according to latitude, which has been employed, a cor- 

 rection which for several reasons is objectionable, the annual 

 isobars for Russia are substantially the same as those published 

 by Mr. Buchan, even though these were confessedly a first ap. 

 proximation, giving only the broad features of the distribution 

 of atmospheric pressure over the globe. Much more is now 

 required than thi=, seeing that the data since acquired would 

 enable us to draw the isobars with a precision sufficient to show 

 not merely their general change of position with season ard lati. 

 tude, but also the exact forms impressed on the curves by their 

 position with reference to large masses of land and water. In 

 solving this problem, what is required from Russia are tables of 

 ttje monthly means of each year during which observations have 

 been made at each station, corrected for instrumental errors now 

 ascertained— tables, in short, similar to those published by Dr. 

 Buys Ballot for many places in Europe, in the Annals of the 

 Dutch Meteorological Institute for 1870. 



Meteorology of Mauritius — The Mauritius Meteoro- 

 logical Results and Meteorological Reports for 1874 and 1875, 

 have been received, which are deserving of special notice from 

 the increased vigour and efficiency with which they show meteo- 

 rological research to be prosecuted in that part of the globe. 

 In addition to the usual elaborate summaries, the Results for 

 1875 contain a noteworthy addition in the form of two Tables, 

 one giving the hourly means of the atmospheric pressure of the 

 months during 1875 deduced from the barograph curves, and the 

 other the same mearrs from the term-day observations made at the 

 observatory from 1853 to 1871. Tables showing the hourly read- 

 ings for each day were prepared but are not printed in "d^^ Results. 

 If this be due to want of funds to meet the expense of publication 

 it is to be hoped that the difficulty will be got over in next pub- 



lication, on account of the great value of such hourly readings in 

 many meteorological inquiries, but more particularly in connec- 

 tion with the gales and hurricanes of the Indian Ocean, which 

 are so carefully detailed by Dr. Meldrum in the Results. The 

 examination of these readings and the hourly observations of the 

 wind could not fail to suggest conclusions of the utmost value in 

 their bearings on systems of storm warnings for tropical countries 

 such as we recently sketched in Nature (vol. xv. p. 261) for the 

 Bay of Bengal. In the Annual Report iax 1875, it is stated in the 

 course of a discussion on sunspots and rainfall, that since the 

 photoheliograph has been in use at the Observatory the sunspots 

 have been compared with the daily weather, and that, so far as 

 the observations have gone, the' results are in conformity with 

 those for longer periods, both the rainfall and the velocity of the 

 wind having been greater when the spots were most numerous. 

 This increase of the velocity of the wind with an increase of 

 sunspots is a point of first importance when viewed in connection 

 with Mr. Lockyer's suggestion that increased sunspot area im- 

 plies increased solar radiation, with Mr. Blanford's confirmation 

 of this idea from an examination of the results of the solar radi- 

 ation thermometers in India, and with the result arrived at by 

 Mr. Clement Ley, showing that with like conditions of pressure 

 the wind's velocity is greatest during those months of the year 

 when temperature is highest. 



Exploring Balloons for Meteorological Purposes. — 

 Since the beginning of February, M. Secretan, the optician of 

 the Pont-neuf, in Paris, has been sending up regularly every day 

 at noon small exploring balloons for the purpose of ascertaining 

 the direction of the several streams of air and the height of clouds. 

 The results are daily published in the Petit Moniteur. The 

 balloons are given gratuitously by the Grand Magazin du Louvre^ 

 and are of india-rubber filled with pure hydrogen. The diame- 

 ter is ninety centimetres. M. de Fonvielle finds by calculation 

 and by several experiment?, that the mean velocity of elevation is 

 about four metres per second. Hence to obtain the altitude o, 

 the clouds it is sufficient to observe the balloon with an opera, 

 glass, to count the number of seconds necessary to lose sight 

 of it owing to the opacity of the clouds," and to multiply the 

 number of seconds by four. It was found that the altitude of 

 clouds varies from 400 to 800 metres, and prospects of fair 

 weather are increased in proportion to the elevation of clouds. 

 The clouds follow the direction of an aerial stream in which 

 they are wholly immersed, and are not placed, as has been 

 repeatedly stated, at the surface of separation. The direction of 

 the air for the first 100 metres is almost always very uncertain 

 and varies according to unknown causes. This shows that 

 anemometers give a very poor idea not only of the velocity 

 but also of the direction of prevailing wind?, and that no real 

 progress is to be expected irr the knowledge of atmospheric 

 calculation as long as meteorologists confine themselves to 

 taking into account anemometrical observations. Very offer, 

 two different streams of air are observed, the lower one extend- 

 ing from roc to 200 or 300 m.etres ; under these circumstances_ 

 the weather seems to be particularly uncertain and unsettle<3 

 Meteorologists, we think, might make use of this method 

 observation with great advantage. 



BIOLOGICAL NOTES 

 x\ CiiYTBiDiUM WITH True REPRODUCTION. — Botanists' 

 are indebted to Dr. L. Nowakowski for a memoir on /l^/r/^/za- 

 gus (ugleuic, in which they will find recorded for the first tim| 

 the whole life-history of one of the most interesting of thegrou| 

 of vegetable parasites known as Chytridia. First described 

 1855 by Bail, who was a pupil at Breslau of the illustrious 

 Cohn, this species has now had all the mysteries of its life 

 cleared up by the researches of Nowakowski, studying at th e ?/<; 

 same university and under the 'same master. The Eug^ense 



