3° 



NATURE 



\July 26, 18 



JO 



towards the northeast, though it still extended from the south- 

 south-east to north-north-west. By ioh. 55m. it had broken up 

 into four irregular streaks of clouds of various breadths and 

 parallel to each other, the only portion of the original arch being 

 a narrow streak extending from the south-east to the meridian, 

 where it faded away. This was the "beginning of the end," 

 for the remnant of the original arch and the other clouds in a 

 short time d'sappeared below the eastern horizon, leaving the 

 sky beautifully clear. 



I should much like to know whether any other observer was 

 fortunate enough to observe this remarkable cloud ; I say re- 

 markable because, though I have been a pretty constant ob- 

 server of the heavens for the last eight years, I have never 

 noticed anything of the kind before. B. J. Hopkins 



10, Malvern Road, Dalston, E., July 24 



Triple Rainbow 



In the afternoon about 5.30 a week or ten days ago, I noticed 

 a rainbow of the ordinary type, and quite complete, which 

 lasted about five minutes ; the portion to the right hand then 

 faded away, as well as the upper and lower portions apparently 

 of that part of the bow visible to the left hand ; but the middle 

 portion of the remainder of the bow divided apparently into 

 three parts, each one complete in their prismatic colouring, and 

 yet none of them parallel to each other. 



There was a slight difference in size, possibly in favour of that 

 portion belonging to the original bow, and which constituted 

 the outermost of the three arcs. 



This portion of the phenomenon lasted f r about five minutes, 

 and was also similarly observed by a gentleman walking with me 

 at the time. 



Unfortunately some large trees prevented us from seeing the 

 lower portion of the three arcs, where presumably they should 

 have been united into one. R. P. Greg 



Coles, Buntingford, Herts, July 23 



A Remarkable Meteor 



In regard to the meteor seen by your correspondent P. F. D. 

 at Hendon on the 6th inst., at 8.53 p.m., in a clear sky and 

 broad daylight, I have the following entry in my diary under the 

 same date : "Meteor going south-east through Cassiopeia at seven 

 minutes to nine ; daylight." It was indeed a remarkable meteor. 

 The sun had set about half an hour. I happened at the time to 

 be looking intently at that part of the north-east sky in which it 

 appeared. What struck me most was the brilliant sparkling 

 silvery li^ht given off by the fragments into which it divided just 

 before disappearing. I estimated that it would strike the 

 horizon about the south-east point. B. G. [enkins 



Dulwich, July 21 



The Function of the Sound-Post in the Violin 



May I be permitted to correct a careless expression in my 

 letter appearing in your last issue on thi-i subject ? The | 

 I refer to is this : " If the bridge [of the violin] were placed 

 near one end of the instrument, the ca e would be different," 

 i.e. the t< ne would be louder. I ought rather to have said : 

 "If the bridge were placed nearer to a firm support, the case 

 would be different. ' The statement is perfectly true as it stands 

 with a sound 1 1. aid which is equally thin all over, or where the 

 edges are thicker than the middle. It is not true with a con- 

 struction like that of the violin, where the edges are extremely 

 thin and flexible. A sonorous wave always transmits itself best 

 from the stronger part of the surface to the weaker. 



R. Howson 



Sand 



Mr. Melvix is at fault in assuming that my paper on sand 

 was "an attempt to distinguish by the aid of the microscope 

 whether sand had been formed by the action of wind or of surf.'' 

 Its primary object was to show that chalk-flint had scarcely any 

 place in its formation; but few particles of it appearing even 

 from the midst of rolled shingle whether that be ancient or 

 modern. Other problems of course may be determined or solu- 

 tions suggested by an extensive examination of ancient deposit", 

 compared witli those now forming. I have shown that quartz is 

 he great staple of "sand." The size of its particles, whether 



rounded by attrition or flat, rough, and angular, must be ac- 

 counted for by observing the conditions under which it extsis 

 in modern formations. A large series is being examined by 

 me, and a record wdl be made of the result. As yet I have 1 o 

 theory whatever. I simply record facts. J. G. Waller 



68, Bohover Street, \V., July 18 



ON MOUNTING AND PHOTOGRAPHING 

 MICROSCOPIC OBJECTS 

 \X/E have received from Mr. E. Wheeler of Tollington 

 *" Road, Holloway, a collection of mounted micro- 

 scopic objects, comprising anatomical, botanical, entomo- 

 logical, and other preparations, and we have much 

 pleasure in testifying to the general excellence of the 

 work. One of the objects — a vertical section of the 

 human small intestine— deserves special mention. It 

 shows the glandular cells especially well. The nerves 

 and ganglia of Auerbach's plexus can be seen, and inter- 

 spersed among the epithelial cells of the villi and Lieber- 

 kuhnian follicles are numerous goblet cells. 



Space will not allow more than a bare mention of the 

 other objects, including a large transverse section of the 

 stem of Lepidodendron from coal, transverse sections of 

 the stems of spruce fir {Abies excelsa) and mare's tail 

 (Hifipitris vulgaris), the former showing resin canals and 

 sections of bordered pits in the wood cells ; Spirogyra in 

 various stages of conjugation, from the first modification 

 of the conjugating cells to the maturation of the zygo- 

 spores ; various Diatomaceas, including the rare Coscino- 

 discus excavata ; injected preparations of intestine of cat 

 and toe of white mouse, and various entomological 

 objects. They are all well prepared, and represent a 

 stock which Mr. Wheeler informs us amounts to fifty 

 thousand objects. 



Although the legitimate use of professionally-mounted 

 objects such as these may tend in no small degree to the 

 diffusion of scientific knowledge, the microscopist who 

 employs his instrument for no better purpose than the 

 examination of bought slides will derive little benefit 

 from the pursuit. He should be able to prepare objects 

 for himself, and although there is abundance of accessible 

 information on every detail of the art, it is believed that 

 there is yet a useful work to be accomplished. By 

 showing the facility with which this can be done without 

 resort to the multiplicity of processes usually considered 

 necessary, we shall endeavour in this article to show 

 how any possessor of a microscope may make for himself 

 preparations which, though they may not equal by many 

 degrees the productions of the best professional mounters, 

 yet have a far higher educational value, as their prepara- 

 tion will afford information which could not be otherwise 

 acquired. 



The necessary materials and instruments are few and 

 inexpensive. For the support of the objects a supply of 

 the usual 3" X l" glass slides with ground edges, and of 

 thin cover glasses (preferably circular) of various sizes 

 should always be at hand. These when bought will be 

 dirty, and it saves time to clean them all at one 

 operation. 



For securing the cover to the slide various cements are 

 used, but of these two only need be mentioned, as they 

 will be sufficient for all ordinary purposes. Gold size is 

 undoubtedly the most reliable cement, but it takes days 

 or sometimes even weeks to harden. It is, however, 

 exceedingly tenacious and tough, and does not become 

 brittle with age. It should always be used in cases 

 where objects are mounted dry or in liquid, but when 

 viscid media are employed, the medium helps to secure 

 the cover, and there is no danger of leakage. Under 

 these circumstances the use of asphalte varnish is recom- 

 mended. The Brunswick black of the oilshops is a 

 common form of this varnish, but is not so good as the 

 preparation supplied by the opticians. When the varnish 

 is to be used, it must be warmed by standing it in a cup 



