August 26, 1886] 
aurora is present ; the stars shine quite bright in this dark sky 
above them. 
Prof. Smyth considers that the night after the aurora of the 
27th the twilight extended over the region ‘‘ aurora-blackened 2 
the evening before. Would not this be owing to the brightness 
of the aurora preventing the twilight from being seen so high 
then simply by contrast? The fact that the dark sky was 
luminous in the spectroscope seems to bear out this. 
I do not understand Prof. Smyth’s suggestion why these 
clouds should never be seen in winter, for any night in the year 
there is a time when the sun is at the same distance below the 
horizon as it is when the bright clouds are well seen. 
Sunderland, August 18 T. W. BACKHOUSE 
Cloud Effect 
A VERY unusual cloud effect was noticed here on the 18th 
inst. at 7.45a.m. The wholesky, especially to the east or south- 
east, was at that time covered with a widespread field of mackerel 
cloud. This field was cut from north to south with a strongly 
defined cleft or narrow line showing the blue sky beneath. It 
was like a crack in the cloudy tissue, and formed a perfect arch, 
whose greatest altitude was not many degrees above the sun’s 
apparent place. It lasted nearly half an hour. There was little 
wind at the time, only a slow motion from the north, but a 
change took place shortly after, when it veered to the south- 
west. E. BROWN 
Further Barton, Cirencester, August 20 
The Crag Deposits on the North Downs 
To students of Tertiary geology, the interest of Mr. Clement 
Reid’s verification of Prof. Prestwich’s judgment of many years 
ago as to the Pliocene age of certain outlying deposits at 
Lenham- is so great that I must crave permission for space for a 
line or two with reference to other similarly situated deposits on 
the North Downs, which have been described as belonging to an 
horizon ‘‘ somewhere between the Chalk and the moon.” The 
deposits to which I refer were described by Prof. Prestwich in 
the 0.7.G.S., vol. xiy., and of his paper Mr. Whitaker made 
free use in preparing the account of these outliers in vol. iv. of 
the ‘* Memoirs of the Geological Survey” (pp. 336-42). The 
idea has been for some time growing up in my own mind, with 
reference to these unfossiliferous outliers, that some of them will 
have to be recognised as remnants of the once more widely 
extended Upper Bagshot Sands. This conclusion is at present 
based mainly on three facts: (1) the literal application of Prof. 
Prestwich’s description of their lithological character to portions 
of those beds ; (2) the occurrence of ‘‘ similar beds on the Chalk 
Downs on the opposite side of the Channel, between Calais and 
Boulogne’; (3) the superposition of ‘‘ analogous strata” on the 
top of Cassell Hill in French Flanders upon the Calcaire grossier 
series, the equivalent of our Middle Bagshot (so-called Brackle- 
sham) Beds. I hope to deal with this more at length during the 
next session of the Geological Society, and only draw attention 
now to the suggestion which I threw out several years ago 
(Proceedings of the Geological Association, vol. viii. p. 170) for 
reasons assigned, that the oldest plateau-gravels of the London 
Basin are probably of Pliocene age. This may possibly have 
escaped Mr. C, Reid’s notice. A. IRVING 
Wellington College, Berks, August 17 
Actinotrocha on the British Coasts 
IN answer to Mr. Cunningham’s letter on the distribution of 
Tornaria and Actinotrocha, I may state that I took Actino- 
trocha in the tow-net at the mouth of this bay on July 31. I 
believe I have found it more than once before on the west coast 
during the last few years, but, not having my note-books with 
me, I cannot say definitely where and when. If I am not 
mistaken, Poronis was found by Dr. Strethill Wright in the 
Firth of Forth, and is therefore known as a British animal. 
Loch Ranza, Arran, August 21 W. A. HERDMAN 
GEORGE BUSK, F.R.S. 
A SINGLE-MINDED, true-hearted man, a warm 
friend, and an able and accomplished naturalist, 
has just passed away from the midst of his family, his 
friends, and his fellow-workers. 
NATURE — 
a 
George Busk was the second son of Mr. Robert Busk, 
of St. Petersburg. He was born in 1807, and at an early 
age gave promise of those tastes and of that aptitude for 
research which, developing with his years, gained for him 
the high position which he was destined to hold among 
the scientific workers of his time. 
After completing his medical education he was ap- 
pointed surgeon to the seamen’s hospital-ship Dvread- 
nought, a post which he continued to hold for about 
twenty-five years. It is these twenty-five years which 
constitute the strictly professional period of his life, and 
which gained for him a place among the most distinguished 
members of his profession as an able, clear-sighted, and 
enlightened surgeon. 
In 1856 he resigned his appointment to the Dread- 
nought, and at the same time decided on retiring from 
professional practice and on devoting himself to scientific 
work. 
Having now leisure for the cultivation of those studies 
which were always dear to him, he threw himself warmly 
into biological work. An excellent and cautious observer, 
it was chiefly to researches on the structure of the lower 
members of the organic world that he now devoted him- 
self, and scarcely a month passed without the periodical 
literature of biology receiving from his labours the record 
of some new and interesting fact. 
About this time he became one of the editors of the 
Microscopical Journal, and the numerous communications 
which appeared from his pen in the pages of that period- 
ical contributed largely to its popularity and success. 
There were few departments of biological science which 
Busk did not enrich by his researches, and we now find 
following one another in rapid succession a long series of 
papers containing the results of his studies among the 
lower groups of the animal and vegetable kingdoms. He 
was a skilful microscopist, an acute and conscientious 
interpreter of the optical expressions of organic form 
presented by the microscope to the observer, and his 
contributions to the transactions of our leading scientific 
societies and to various natural history journals have 
advanced our knowledge of some of the simple unicellular 
plants, of the Infusoria, the Hydroida, the lower Vermes, 
and above all of the Polyzoa, to an extent which those 
who have worked in the same fields can fully appreciate. 
In 1856 appeared his article ‘‘ Polyzoa”” in the English 
Cyclopedia, In this admirable article we have an ex- 
haustive account of the structure of the Polyzoa, while it 
contains the first satisfactory attempt at a scientific 
arrangement of the group, and proposes for the first time 
the employment of certain systematic characters which 
are now universally accepted as offering the only legiti- 
mate bases of a philosophical classification. 
Soon after this he undertook the labour of drawing up 
an illustrated descriptive catalogue of the Polyzoa con- 
tained in the collection of the British Museum, and 
brought to bear on the descriptions and systematic 
arrangement of the species those principles whose sound- 
ness he had already established. There was thus placed 
in the hands of the student a work of great value, with 
which no investigator of the group can afford to 
dispense. 
On the return of H.M.S. Rattlesnake from its explora- 
tions in the Australian seas under Capt. Owen Stanley, 
the collections of Polyzoa and Hydroids made during the 
voyage were placed in Mr. Busk’s hands for examination 
and description. His report on the new species thus 
obtained is published in the narrative of the voyage, 
and forms an important addition to our knowledge of 
these animals. 
Among the facts of anatomical interest which have 
been successfully worked out by Busk in the organisation 
of the Polyzoa, his demonstration of the structure of the 
avicularia and vibracula deserves special mention. He 
has given by far the best account which had been hitherto 
