January 28, 1892] 



NA TURE 



301 



the Ben — a conclusion in keeping with the result obtained 

 at low level. 



It is concluded from the observations that high winds 

 reduce the transparency of the air. In Part I. this con- 

 clusion is indicated, and the observations of 1890 confirm 

 it. It is pointed out that whenever the wind was high, the 

 air was unduly thick for the number of particles and the 

 humidity. This is thought to be due to high winds carry- 

 ing large particles, and mixing the lower stratum of im- 

 pure air with the purer upper air. The inequalities in 

 the density of the different parts of the air produced by 

 imperfect mixing will also reduce its transparency. 



The Alford observations for 1890 show that the air was 

 occasionally purer and the maximum a little higher in 

 that year than on the previous visit. Whenever the wind 

 blew from the south, it brought polluted air to this station, 

 as it came from inhabited areas ; and when the wind was 

 northerly the air was pure. The number of particles was 

 as low as 127 per c.c. with a north-west wind, while it 

 was as high as 6800 per c.c. with a south wind. 



An ascent of Callievar was made in 1890 also. On the 

 first visit the air was clear, and the Cairngorms and Loch- 

 nagar were clearly seen. The number of particles was 262 

 per c.c, and rose in the afternoon to 475 per c.c. ; but 

 on the second visit the air was thick, and only a faint out- 

 line of the Cairngorms was occasionally seen, while Loch- 

 nagar was quite invisible. The number of particles was 

 710, and rose in the afternoon to 1575 per c.c. 



The air on this occasion was very irregularly hazed, not 

 being equally transparent in all directions. One mass of 

 air darkened the view to the west, passed over the hill-top 

 and darkened the view to the east. Before this impure 

 mass of air arrived at the hill-top the number of particles 

 was 710, while it was passing the number rose to 1575, 

 and after it had gone east the number fell to 1050 per c.c. 

 During these observations the humidity remained con- 

 stant. The variations in the transparency were therefore 

 due to variations in the amount of dust. 



The condition of the air during the exceptionally warm 

 February of 1890 was tested at Garelochhead on the 27th 

 of the month. Previous to that date the weather had 

 been very warm, temperatures of 50° and 60° having been 

 frequently recorded in our area, and even 64" was 

 observed in more places than one. The result of the 

 tests showed the air to be remarkably full of dust. During 

 the visit to this station in the end of January 1889, the 

 maximum number of particles observed was 2360, and that 

 was the only occasion on which it was over 1000 ; whilst 

 on the first day of the second visit the smallest number 

 observed was 7250, and other readings gave nearly 10,000. 

 During this warm period the air was always impure, and 

 had much the same appearance as it had on the 27th. 

 The cause of this great amount of impurity was the pre- 

 sence of an anticyclone lying over Europe, giving rise to 

 southerly winds over our area. The local winds were, 

 however, very light and mi.xed, and there was no general 

 circulation of the air ; the dust impurities therefore 

 accumulated, and, as the figures show, became very great. 

 On the 28th, the day after the air was tested, a depression 

 appeared off the north of our islands, and the isobars 

 were closing in and westerly winds were beginning to 

 blow. With this change the dust began to fall, and was 

 as low as 1750 per c.c. on the 28th. On March i and 2 

 the isobars closed in still further, the winds freshened, 

 and the dust fell to 51 per c.c, or ^\^ of what it was on 

 February 27. During the 3rd, 4th, and 5th, the wind 

 remained in the north-west, and the amount of dust was 

 very small. 



Certain relations between isobars and dust are pointed 

 out. With regular isobars for westerly and northerly 

 winds the air is pure, and the closer the isobars the purer 

 is the air ; whilst isobars for southerly or easterly winds, 

 even though close, do not indicate pure air. From these 

 facts it is shown that an estimate of the amount of dust on 



NO. 1 161, VOL. 45] 



any day can be made from an examination of the weather 

 charts made on and previous to the day selected. 



The relation between the amount of dust and the 

 temperature is discussed, with the view of finding whether 

 the observations made in 1890 confirm the conclusion 

 arrived at from the previous records. That conclusion was 

 that a great amount of dust increases the day tempera- 

 ture and checks the fall of temperature at night. The 

 records of temperature and radiation made at Kingairloch 

 in 1890 are of no value, owing to the weather being 

 always under the influence of cyclones, so that there was 

 an absence of clear skies, and the temperatures were re- 

 gulated by what the winds brought, and were but little 

 influenced by local conditions. But, as already stated, 

 the dust at this station was exceedingly low in 1890, and 

 the temperature was also exceptionally low. 



The Alford observations, however, are not open to the 

 same defect, as the weather was suitable for the purpose. 

 These observations point to the same conclusion as that 

 arrived at in 1889. The highest maximum temperatures 

 were recorded on days of high dust, and the lowest 

 minimum when the dust was at a minimum. 



The observations made at Garelochhead also support 

 the same conclusion. Towards the end of February the 

 amount of dust was great, and from the meteorological 

 report it will be seen that the temperature was above 

 the mean, and was frequently very high. Again, when 

 the westerly winds swept away the great impurity, they 

 brought with them a high mean temperature. But after 

 the winds ceased to blow, the pure air brought to our 

 area by them seems to have allowed radiation to act 

 freely, as the air then rapidly cooled, and the tempera- 

 ture became exceedingly low, as much as from 8 to 

 1 1 degrees below the mean in some stations in Scotland. 

 The Ben Nevis observations show that during this ex- 

 ceptionally cold period the air was remarkably free from 

 dust. 



JOHN COUCH ADAMS. 



T T is with deep regret that we record the death of Prof, 

 A Adams, who will always hold an eminent place in 

 the history of astronomical science. As he is included 

 in the list of our " Scientific Worthies," we have already 

 given an account of his career (vol. xxxiv. p. 565). It is 

 only necessary for us now, therefore — as in the case 

 of Sir George Airy — to note some of the leading facts of 

 his life and work. 



He was born at Lidcot, near Launceston, in Cornwall, 

 on June 5, 1819. He received his early education at the 

 village school and at Devonport, where he gave evidence 

 of his remarkable faculty for mathematical and astro- 

 nomical study. In October 1839, he entered at St. 

 John's College, Cambridge; and iu 1843 he graduated 

 as Senior Wrangler and first Smith's Prizeman, becoming 

 shortly afterwards a Fellow and tutor of his College. 



Both before and after taking his degree he was fascin- 

 ated by a problem which was at that time profoundly in- 

 teresting astronomers — the irregularities shown by the 

 planet Uranus in its motion. Its orbit differed from the 

 elliptic path which an undisturbed planet would have 

 pursued ; and as the deviations could not be explained 

 by the influence of the other known planets, it was 

 supposed that there must be a more remote planet which 

 had not then been observed. To the search for this un- 

 known planet Adams devoted all the energies of his 

 mathematical genius, and everyone knows the brilliant 

 success with which his labours were crownt d. His solu- 

 tion was communicated to Prof. Challis in September 

 1845, and to the Astronomer-Royal in the following 

 month. We need only refer to the facts that similar 

 work was done in 1846 by Leverrier ; that the French 

 astronomer's results, unlike those of the English investi- 



