August 8, 1889] 



NATURE 



35 



tions made by him and Mr. Omond, the numbers varied from 

 350 per cubic centimetre about noon to 500 at 3 p.m. The 

 purest air previously examined by Mr. Aitken was on the Ayr- 

 shire coast, and gave 1260 dust particles to the cubic ceniimelre. 

 It is, of course, premature to draw conclusions from these obser- 

 vations, but it may be suggested that extended observation will 

 in all probability establish the fact of the singular purity of the 

 air at this height, as compared with that at lower levels ; and 

 that the numbers of dust particles will be greatest at the Obser- 

 vatory in that part of the day when the ascending currents up the 

 heated sides of the mountain are strongest. 



Reference was made in our last issue (p. 326) to the drought 

 on the top of Ben Nevis in June last. In that month the hours 

 of sunshine registei-ed by the sunshine recorder were 250, a number 

 considerably in excess of any previous month, the highest 

 having been 206 hours in June 1887. With the early disappear- 

 ance of the snow and strong sunshine of June, such vegetation 

 as is found at these heights is well forward. On July 22, fine 

 specimens of Sihne maritima, about 8 inches in height, well 

 grown, with abundant flowers, many of them in seed well 

 matured, were gathered on Cairn Dearg, one of the lower 

 heights of the mountain, at a height of 3800 feet above the sea. 

 In Hooker's " Flora of the British Islands," the limiting height 

 of this plant is given at 3000 feet. 



The Report of the Director of the Hong Kong Observatory, 

 for 1888, has been issued. It is an interesting and exhaustive 

 document. In reference to thunderstorms in the colony during 

 the past five years, Dr. Doberck states that they are most 

 frequent in May, and that they have not occurred in November, 

 December, and January. They seldom happen in February. 

 With reference to the daily variation, they are more frequent at 

 night than during the day-time in the proportion of three to two. 

 They appear to be most abundant about i a m. , and least so about 

 8 a. m., in the proportion of about two to one. During the past 

 year the temperature was on an average higher than in previous 

 years, and rose higher than before on hot days. This appears to 

 have been at least partly due to a more southerly direction of the 

 wind, but the temperature has been rising on the whole since 

 1884. Whether this is periodical remains to be investigated. 

 The Director thinks there are fair prospects of finding it is so. 

 The past year was more damp than usual, the rainfall was heavy, 

 and the mean barometer below the average. The amount of 

 sunshine was less, and the cloudiness greater than usual. It is 

 generally considered to have been an unhealthy year. 



Science says that in 1887-88 the courses in astronomy at 

 the Johns Hopkins University were so extended as to justify its 

 being chosen as a princijial subject by candidates for the degree 

 of Doctor of Philosophy. A small observatory has been erecttd, 

 and is fitted up with a meridian circle by Fauth and Co., a port- 

 able transit instrument by Troughton, a clock, a chronograph, 

 and other subsidiary apparatus. In the dome of the physical 

 laboratory is mounted an equatorial of 9^ inches aperture, so 

 fitted that the student can learn to make the usual determina- 

 tions with the largest instruments of ths.t clas«. The work in 

 astronomy consists of a study of the history and practice of the 

 subject, supplemented by instruction in the use of the instru- 

 ments, and exercises in astronomical computation. During the 

 year 1889-90 the courses are intended to cover a wider range of 

 individual subjects than usual. 



The Royal Society of New South Wales offers its medal and 

 a money prize for the best communication (provided it be of 

 sufficient merit) containing the results of original research or 

 observation upon each of the following subjects. To be 

 sent in not later than May i, 1890 : — The influence of 

 the Australian climate (general and local) in the develop- 



ment and modification of disease — the Society's Medal and 

 £2$ ; on the silver ore deposits of New South Wales — the 

 Society's Medal and £2^ ; on the occurrence of precious stones 

 in New South Wales, with a description of the deposits in which 

 they are found — the Society's Medal and ^25. To be sent in 

 not later than May i, 1891 : — The meteorology of Australia, 

 New Zealand, and Tasmania — the Society's Medal and £2^, ; 

 anatomy and life- history of the Echidna and Platypus — the 

 Society's Medal and;i^25 ; the microscopic structure of Australian 

 rocks — the Society's Medal and £2^. The competition is in 

 no way confined to members of the Society, nor to residents in 

 Australia, but is open to all without any restriction whatever, 

 excepting that a prize will not be awarded to a member of the 

 Council for the time being ; neither will an award be made for 

 a mere compilation, however meritorious in its way. The com- 

 munication, to be successful, must be either wholly or in part the 

 result of original observation or research on the part of the 

 contributor. 



At a recent meeting of the Genevan Society of Physics and 

 Natural History, M. Mallet exhibited two balls of almost per- 

 fect sphericity, about 4 inches in diameter, one black, and of 

 vegetable origin, the other white, and of mineral origin, but both 

 produced by a mechanical movement. The black ball had been 

 found with another in a piece of oak which had long served as 

 the shaft of a mill-wheel. A cavity having formed in the wood, 

 through disease or the work of some insect, the dust of the wood, 

 with acquired moisture, had been rolled into this spherical form, 

 growing in size, like a snowball (a slow process of many years 

 probably, as the wheel was very old). The white ball, a cal- 

 careous pebble, was found with many others in a grotto traversed 

 by a torrent which flowed into the Rhone. 



Four years ago a li^ht-ship was stationed in the Baltic, 

 between the Islands of Bornholm and Riigen, and the currents 

 there have been measured on 294 days in a year, every two 

 hours, with interesting results (described by Herr Dinklage in the 

 Annalen der Hydrographie). It is found that the currents vary 

 most irregularly in direction, strength, and duration, but in 

 most cases follow the prevailing winds (of which the westerly 

 are the most frequent). Currents which did not diverge more than 

 90° from the wind's direction being counted as similar in direc- 

 tion, 86 per cent, were of this nature. The relation becomes 

 more pronounced when only winds and currents above a certain 

 limit of force are considered. A sudden change in direction of 

 wind is soon followed by a change in that of current. The effect 

 of wind direction on current direction is certainly apparent th« 

 first day, and to a depth of at least 5 metres. The direction of 

 current rarely coincides exactly with that of wind, and diverg- 

 ence to the right is distinctly more frequent than divergence to 

 the left. As this cannot be attributed to the form of neigh- 

 bouring coasts or to the circulation of winds (for winds in our 

 latitudes turn mostly the other way), the author regards the 

 effect as due to the rotation of the earth. 



The Northern Lighthouse Board have adopted Priestman's 

 oil engines for blowing fog signals in preference to steam or gas 

 engines. A great saving is thus effected in first cost, no chimney 

 being required as in the case of a steam engine, nor gas works, 

 which would be needful if a gas engine were adopted. 



The first part of the Journal of the College of Science of the 

 Imperial University of Japan, which has just been published, 

 contains two papers illustrated by numerous excellent plate?. 

 The first is by Prof. Matsujiro Yokoyama, on the subject 

 of "Jurassic Plants from Kaga, Hida, and Echizen," three 

 provinces on the v\ est coast of Japan. It is a valuable contribu- 

 tion to our knowledge of the fossil flora of Japan, a subject 

 hitherto little investigated. Prof Yokoyama's spec mens were 

 collected, for the most part, by the Geological Survey of Japan. 



