May $i, 1883] 



NATURE 



103 



Riviera, to the absence of sunspots." My observations prove 

 only the coincidence of a sudden and unprecedented visitation of 

 cold, with an absence of sunspots (the more remarkable as oc- 

 curring during a maximum sunspot period) ; and the further 

 coincidence of a progressive rise in temperature with the return 

 of the sunspots ; but I add, "These observations are too few 

 and too imperfect to warrant any decided conclusions ; but 

 they add to those already made in evidence of the connection 

 between the absence of sunspots and the diminution of terrestrial 

 heat ; and I trust they may be followed by further and more 

 exact investigations, to determine the influence of our great 

 luminary on the weather and climate of the world." 



It does not appear to me that Dr. Woeikof has succeeded in 

 establishing a parallel between Cannes and Suchum-Kale on the 

 Black Sea ; which, however sheltered locally, must, far more 

 than Cannes, be liable to chilling influences in the cold winds 

 from the lofty mountains and vast elevated steppes to the north, 

 extending even to the Arctic regions. Therefore the fall of 31° 

 below average in March, 1874, might not be extraordinary, even 

 in a year with a considerable number of sunspots. It is not 

 stated that the spots continued in this particular month. 



The case of Cannes may be thus stated : With a climate 

 usually so mild in winter that frost and snow are of rare occur- 

 rence ; and this winter, with slight frost only three times before 

 February, and none at all in that month, the average minimum 

 being 44°, — on March 7 minimum fell to 36°, with a heavy fall of 

 snow; and on the 8th, 10th, nth, and 12th, the minimum fell 

 further to 27°7, 27°, 24°i, 25°7. The sunspots, which had been 

 observed by my friend, Mr. Campbell, of Islay, to be large and 

 active until February 26, suddenly disappeared, and on February 

 28 and March 3 I found no spots ; on the 10th and nth only one 

 or two small spots. On the 12th they began to appear in 

 numbers, with a large oval facula. From that day they con- 

 tinued to increase, and the temperature gradually rose to the 

 ordinary average. 



I will not occupy space with further arguments, but I will 

 merely state some more facts with regard to the extraordinary 

 intensity and universality of this invasion of cold, and my further 

 observations of the sunspots. At my villa at Cannes, which is 

 favourably placed in position and shelter, the register did not 

 fall so low as in other parts. At Dr. Frank's villa, Grand Bois, 

 more open to the north (thermometer in louvred box, a metre 

 above ground), the minima were : March 7, 27° ; 9, 25°'2 ; io, 

 21°; 11,21°; 12,20°; 13,25°. At Villa Beaulieu, more shel 

 tered (therm, abo in louvred box), minima were : March 7, 29 ; 

 9, 27°; 10, 25°; 11, 26°; 12, 28°. Dr. de Valcourt's minima are 

 somewhat higher ; but he adds this note : " La periode de froid 

 du 7 au 14 Mars, 1883, a ete tres remarquable ; elle est unique, 

 depuis que Its observations reguheresont elerecueillis a Cannes." 

 Where instrumental records are wanting, we refer to the report 

 of the "oldest inhabitants," and learn that there has not been a 

 cold so severe or destructive to oranges and olives since the 

 year 1820. 



Extraordinary and intense as was this invasion of cold, it 

 might have been supposed due to local or regional causes only, 

 had it been confined to Cannes and its neighbourhood. In my 

 former paper I stated that I was not informe 1 how far the cold 

 had extended to other countries and latitudes. We still need 

 further exact information on this point, but what has already 

 reached us goes far to prove that the cold was universal, and not 

 limited to a region. In England, Mr. Thomas Plant writes to 

 the Times from Moseley, Birmingham : — " After one of the 

 mildest winters registered in the Midland Counties, the month 

 of March, which is generally expected to be the beginning of 

 spring, has been colder this year than any corresponding month 

 for 3S years." "When we consider the pouerof the sun in 

 March, as compared with December, January, and February, 

 then we can reali-e some idea of the prolonged and most ab- 

 normal cold of the month now ended." By private information 

 _ I learn that at the same time, in Stockholm, Centigrade's ther- 

 mometer fell 13°, and at St. Petersburg iS°, below freezing. 

 Unu ually intense cold in March is also reported from Canada. In 

 the south we hear of snow and frost in South Italy, Sicily, 

 Algeria, Egypt, and even Nubia. Later still there have been 

 reports of snow on the mountains of Madeira and California, 

 v> here it had never been seen before. 



Since March 19, the date of my former letter, I have been 

 able to make sketches of the sun's position on 49 days. 1 Of 



1 I use only a modest achromatic of 32 inches focus, and i\ inches aper- 

 ture, which, projecting the solar image on a white card, exhibits the spots 

 with umbra and penumbra, and the facula;, sufficiently for this purpose. Of 



these observations the following summary may suffice. In 

 number the spots varied from 3 to 18 ; the larger showing, 

 more or less, holes or clefts of central umbra, with fringe of 

 penumbra. Facula;, or clouds of whiteness, were often seen 

 around the larger spots. The spots varied in number and form 

 from day to day ; and although the same large spots and even 

 groups could be traced for several successive days, they never 

 retained the same aspect during the whole period of the sun's 

 semi-rotation. On April 17 the spots were at their maximum ; 

 in number IS, in three groups. During this period, from March 

 19 to April 19 — thirty-one days — the mean minimum temperature 

 was 46°2, mean maximum 57°'9- 



From April 20 to May 7 there was considerable diminution of 

 the spots ; numbers not exceeding 8 ; and on May 7 there was 

 only one large spot, with surrounding facula. The mean tem- 

 perature of these seventeen days was — minimum 49° "8, maximum 

 60 . 



From May 8 to 16 spots were few, from 2 to 8 ; but two of 

 them were very large, with umbra and penumbra and sometimes 

 adjoining facula;. The mean temperature of these nine days 

 was — minimum 52°'7, maximum 63°'8. 



Here my observations terminate, as I left Cannes on the i6tb, 

 and have no means of observing in London, even if the atmo- 

 sphere permitted. But I conclude by strongly commending the 

 attentive study of the sun not only to astronomers and physicists, 

 but also to practical meteorologists, as an interesting and not 

 difficult addition to their work of observation, and one likely to 

 supply information concerning the most important factor in the 

 problems of weather and climate. C. J. B. Williams 



47, Upper Brook Street, May 25 



The Soaring of Birds 



My thanks are due to Mr. R. Courtenay for the notice he has 

 taken (Nature, vol. xxviii. p. 28) of my letter on the Soaring 

 of Birds (vol. xxvii. p. 592). It is a great satisfaction to me to 

 find my general conclusion supported by his observations. As 

 to the possibility of a soaring bird utilising a downward current 

 of air, I stand corrected. There is no difficulty in agreeing with 

 Mr. Courtenay that the bird, finding itself in a downward 

 current " will descend swiftly o as to acquire the nece-sary 

 impetus for a rapid escape;" — that is to say, it will seek to make 

 the best of a bad bargain. But it is not so easy to see that the 

 bird, in a current approaching the perpendicular, will "acquire 

 an impetus much more than compensating for the slight loss of 

 elevation ; " — that is, will actually make a profit out of a seem- 

 ingly adverse condition. 



This paradox, however, becomes more acceptable by the aid 

 Of an illustration : — A marble held lightly just within the rim of 

 a hemispherical bowl, if let drop, will barely reach the opposite 

 rim, but, if struck sharply downward, will run up the opposite 

 side and leap up above the opposite rim. In line manner a 

 bird, struck by a downward current as by a hammer-stroke, may 

 speedily acquire a downward velocity greater than that due 

 (under gravity) to the height through which it has descended ; 

 and may therefore rise, if it can escape from the downward 

 current into a horizontal (or a fortiori into an upward) current, 

 to a greater height than if it had fallen from the same starting- 

 point through still or horizontally-moving air. 



1 am very much obliged to Mr. Courtenay for pointing out 

 this interesting result. It gives completeness to the theorem, 

 which n iw stands thus : that any alternations in the strength or 

 direction of air-currents can be so utilised by birds as lo enable 

 them to soar. Hubert Airy 



Woodbridge, May 25 



The Zodiacal Light 



The phenomenon to which your correspondents allude, under 

 the head of zodiacal light, was seen by me in the month of 

 April, 1852. At the time I wrote a letter to the Times, in 

 which I suggested it might be caused by the reflection of the 

 sunlight at the surface of two masses of air of different densities, 

 however irregular the bounding surface might be, in the same 

 manner as the line of l'ght seen reflected between the observer 



course a more powerful instrument would show a great deal more, both in 

 number and in construction <>f the spots. For instance, on April 17, when I 

 made nut 18 spots, Mr. Campbell's solar image exhibited 104, with 

 marvellous variety in the larger spots, and in the dome-like expansion of the 

 adjoining faculae. But these details, so deeply interesting in heliography, 

 are not wanted for meteorological purposes. 



