544 



NA TURE 



[April 5, 1894 



excellent forestry school at Zurich. In France not only does 

 the State manage its own forest property in approved manner, 

 and supervise the management of forests belonging to com- 

 munities and other public institutions, but it extends its control 

 over private forests liy forbidding any clearing except with the 

 consent of the foresf administration. 



Sir Robert Ball commences a series of articles on "The Great 

 Astronomers " in Good Words, the subject of his sketch this 

 month being Tycho Brahe. Dr. Dreyer's book on "The Life 

 and Work of Tycho Brahe " has furnished the author with most 

 of his facts, so the article can hardly be abstracted, and there is 

 nothing in it to comment upon. Mrs. Percy Frankland con- 

 tributes an article entitled " Half an Hour with the Microbes," 

 and manages to compress a large amount of information in a 

 few pages. An article by Sir Herbert Maxwell, headed 

 " Assisted Sight," will be found interesting to Selbornians, for 

 it deais with the sights of bird-life and movement which a spy- 

 glass reveals to him who will be at the trouble to carry it. 



A passing notice must suffice for the other magazines received 

 by us. 



In Longman s, Mr. C. T. Buckland, a cousin of the late 

 Frank Buckland, describes some of his personal experiences 

 with alligators, and W. Schooling recounts some of the myths 

 and marvels concerning the Pleiades. Lord Lilford writes upon 

 the destruction of wild birds in the National Review. He con- 

 siders that the legal protection of eggs under specific names is 

 impracticable, if not utterly impossible. The National also 

 contains an article of interest to nature lovers, by " A Son of 

 the Marshes." Two articles of more or less scientific interest 

 appear in Chambers's Joit}-nal, one on " The Smoke Problem," 

 the other on the new powder, Amberite. Mr. Phil Robinson 

 contributes to the Contemporary a description of natural objects 

 in spring, in which poetical fancy is happily blended with 

 scientific observation. Serpent-worship, and the serpent's 

 strange appearance and manner of progression, is Mr. W. H. 

 Hudson's theme in the Fortnightly. Mr. R. B. Anderson 

 describes, in Scribner, a winter's journey up the coast of 

 Norway, and Mr. Morley Roberts writes on cannibalism in the 

 Iiu7nanitariati. 



DUST AND METEOROLOGICAL 

 PHENOMENA.^ 

 TN this communication are given tables containing over looo 

 observations of the dust particles in the atmosphere, along 

 with simultaneous observations on other meteorological 

 phenomena, made by the author during the years 1S91, 1892, 

 and 1893. In Parts i. and ii. on the same subject are nearly 

 500 similar observations, made at the same places, during the 

 two preceding years ; so that there are in all now over 1500 

 observations of atmospheric dust, to produce which required 

 the testing of over 15,000 samples of air. With such a number 

 of observations it seemed not unreasonable to expect that more 

 definite results could now be worked out than were possible 

 before. 



At the beginning of the paper reference is made to obser- 

 vations made in the south of France, at Hyeres, Cannes, and 

 Mentone. After this the observations made at the Italian 

 lakes are described. At none of the places in these districts 

 was very pure air ever met with. No air with a smaller num- 

 ber of particles than 600 per c.c. was tested. 



At Baveno, in addition to the usual test at low level, a 

 number were made at different elevations on the slopes of 

 Monte Motterone, with the following results. With the wind 

 blowing up the slopes, the means of seven observations gave the 

 following number of particles per c.c. at the different levels : — 



At low level 

 4857 



At 1000 feet. 

 4750 



At 1500 feet. 

 3430 



At 2000 feet. 

 3125 



And the mean values of eight observations when the wind did 

 not blow up the slopes : — 



to 0*64 of the number at low level, while if the wind was from 

 other directions it was reduced to 0^3. 



The observations made on the Rigi Kulm during three visils, 

 of a week each, in the different years are then discussed, and 

 the conditions existing during each day described separately, 

 along with the different meteorological phenomena witnessed 

 on the different days. The conclusion arrived at in the pre- 

 vious visits as to the exaggerated descriptions given by many 

 writers, of the beauty of the colouring on earth and sky seen at 

 high level at sunrise and sunset, is entirely confirmed. During 

 the visit, in the five years no colouring at sunrise or sunset has 

 been vvitnessed from the Rigi equal to what is frequently seen 

 at low level. 



The observations show that the sunset colours depend very 

 much on the amount of dust in the air. When the atmosphere is 

 comparatively free from dust the colouring is cold, but the 

 lighting is clear and sharp ; and when there is much dust, 

 there is more colour on the mountains and clouds, and in the air 

 itself, and the colouring is warmer and softer. At high level 

 the colouring is not only more feeble, but it is also of shorter 

 duration. A thick veil of haze seemed to hang in the air between 

 the observer and the mountains on all days when the number 

 of particles was great, and it became very faint when the 

 number was small. 



The paper then proceeds to investigate the effect of the direc- 

 tion of the wind on the number of particles at this station, and 

 discusses the conditions with the aid of the dust observations 

 and the weather charts of Switzerland — the general air calcu- 

 lation over Switzerland being obtained from the reports of the 

 high level observatories, namely the Santis, St. Gothard, and 

 Pilatus, and low level currents from the reports of the low 

 level observing stations. The results of this investigation are 

 summed up in two tables. In one of these tables are given the 

 highest and lowest numbers observed when the wind was south- 

 erly and blew from the pure area of the Alps ; and in the other, 

 the observations when the wind was from the inhabited parts 

 of Switzerland. The following are the means of all the obser- 

 vations : — 



The condition of the air on the occasions of the different 

 visits to the Rigi varied greatly. During the visit in 1889, the 

 wind always blew from the Alps, the number of particles was 

 low, and air very clear. During the visits in 1892 and 1893, the 

 wind never blew steadily for any length of time from the pure 

 direction, the air was always much hazed, and the number of 

 particles great. 



The effect of the amount of dust on the transparency of the 

 air on the Rigi is then discussed. The above table, showing 

 the effect of the direction of the wind on the number of particles, 

 also shows the effect of the dust on the transparency. On all 

 days when the wind was southerly, and the number of particles 

 low, the air was clear, or very clear ; whereas when the wind 

 blew from the plains, and the number went high, the air was 

 always greatly hazed. The effect of the dust on the trans- 

 parency is then shown in another way, the result being given 

 in the following table, in which are entered the number of times 

 Hochgerrach was visible, and the condition of the air at the 

 time as regards haze, dust, and humidity : — 



Number of times 

 visible. 



Amount of haze 



on Hochgerrach. 



\Xo\ 



a 



4 



Just visible 



Number of par- 

 ticles per c.c. 

 326 to 850 



1375 to 1575 

 1825 to 2050 



Wet bulb 

 depression. 



3° to 10" 

 6"-S to 8' 

 4' to 6°'5 



Thus with the wind blowing up the slopes, and carrying up 

 the impure air, the amount of dust at 2000 feet was only reduced 



1 Abstract of paper read before the Royal Society of Edinburgh, by 

 John Aitken, F.R..S., on February 19. (Communicated by permission of 

 the Council of the Society.) 



NO. 1275, VOL. 49I 



Hochgerrach is situated at a distance of about seventy miles 

 from the Rigi, in an easterly direction ; its viability, therefore, 

 may be taken as an indication of very clear air. The above 

 table shows that it was visible on thirteen occasions. On eight 

 of these it was only from 1 to h hazed, and the number of par- 

 ticles was at a minimum. The table also shows that as the 

 number of particles increased the haze also increased, and at 

 last the mountain became invisible when the number went a 

 little over 2000 per c.c. As the number of particles frequent y 

 remained above 2000 for days at a time, Hochgerrach could 

 only be seen at intervals. 



The paper then passes on to consider the daily maximum on 



