August, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



507 



in the '■ ozobrome " methods, the result depends upon 

 development in the same sense in which the ncgatixx; 

 is developed, and while this may sometimes be an ad- 

 vantage to the skilled worker, it renders all sorts of 

 errors possible. This radical difference must ever be 

 borne in mind. 



Specially Scnsilhcd Plates. — Since my notes of two 

 months agoi were printed, 1 have received from Mei;srs. 

 Wratten and Wainwright samples of their specially 

 sensitised plates. There are four kinds, all essentially 

 different from the ordinary " isochromatic " plates, in 

 being so- much more sensitive to red, and therefore to 

 yellow, that yellow colour screens, that generally need 

 the exposure to be increased to ten times, with these 

 plates require only about a doubled exposure. TTie 

 " verichrome '' plate may be developed in a deep red 

 light, but no light is safe for the others, except that a 

 very weak green light might be used with the 

 pinacyanol-bathcd plates. These last are extra- 

 ordinarily sensitive to red. The pinachrome-bathed 

 plates are very sen.sitive to red, but le.^s than the 

 pinacyanol plates, and they are more sensitive to^ green. 

 Without doubt, the most u.seful for general purpo.ses 

 are the " verichrome " plates, for moderate red sensitive- 

 ness, and the " panchromatic " plates, if extreme red 

 sensitiveness is wanted, and as these arc not called 

 bathed plates, I presume that the emulsion is .sensitised 

 before the plates are coated. The plates are all of high 

 general sensitiveness, the H and D' figure ranging be- 

 tween 100 and 200, and they all give good gradation, 

 liach box contains a card that gives the .sensitiveness 

 on the H and D, Watkin's and Wynne's systems, the 

 time required for development at 50", 65', and 80° F., 

 besides other information. 



Received. — Messrs. Taylor, Taylor and Hobson 1 ive 

 .sent me a flexible releasing arrangement, on the Bowden 

 wire principle, for the shutter referred to last month. 

 It is of excellent design and workmanship, and is at- 

 tached to or removed from the shutter in a moment b\' 

 a bayonet joint. Such releases are much i.01 be preferred 

 to pneumatic balls, because they have no indiarubber 

 in them to perish, and they give a positive rather than 

 an elastic push. I have so far found only one disad- 

 vantage, namely, that if a comparatively short bend is 

 necessary, as may be in sonic hand cameras, it will 

 cause too much friction in a Bo-wden wire before it 

 interferes in any way with the flow of air through a 

 tube. 



The " Inip<Ti.il llandlxxik for igo6." is (-hicfly .-i col- 

 lection of useful hiiUs and dal.i for tho.se v\ ho use 

 photographic materials. It includes :i price list of the 

 Company's manufactures, and the recommended 

 formulae for their treatment. 



The" I'hoto-Mini.-iturc " for last December, piicf 6(1., 

 is iust to hand. It is a useful little \'olunic on hromid',' 

 |-,rinting .-nid cnlai'ging. 



Vitality of SeeJs. 



To the disputed question of the vitality of dried or buried 

 seeds a new contrihutidn has been made by M. Flichc, a 

 French botanist. In the Forest of I lane some years ago 

 he was astonished to find large quantities of a plant called 

 cypress-spurge, or wolf's milk, in blossom. It is a ])lant 

 well known in Italy, but not indigenous to France. Two 

 venrs l;iter the plants entirely disappeared. Similarly another 

 growth, in another clearing of the forest, was une.-irthed, 

 and this in its turn flourished and disappeared. The obvious 

 bot.nnieal reason for the disa])pearance of a plant is that it 

 is choked in the struggle for life by the existence or over- 

 growth of other plants better suited by the environment ; 

 .and that the cypres.s-spurge, not finding itself able to cope 

 with its surroundings, disappeared. 



ASTRONOMICAL. 



By Charles P. Butler, .\.K.C.Sc. (Lend.), F.R.P.S. 

 Origin of Lunar Formations. 



In- the annual report of the Paris Observatory for 1905 

 M. Loewy briefly discusses the results of a very thorough 

 investigation of the lunar photographs which have been 

 obtained with the great equatorial Coude, in preparation of 

 the gth volume of the Atlas Photographique de la Lune. 

 Endeavouring to find possible causes of the peculiar forma- 

 tions of seas and mountains, three distinct sources^ are 

 tabulated : — (a) They may be due to meteor swarms circu- 

 lating round the "sun ; (6) projections from terrestrial 

 volcanoes ; (c) thev mav have been detached from the earth 

 while still fluid, and have circulated round in orbits only 

 slightly differing from that of the moon. Examining these 

 in detail, the first two are found to be incapable of explain- 

 ing the known phenomena, and it is concluded that the third 

 suggestion is the more probable, the annexation of the ring 

 of satellites at intervals, while the surface of the moon was 

 sufficiently condensed to enable the masses to become at- 

 tached without being entirely absorbed and their individual 

 forms eliminated. 



Return of Finlay's Con\et. 



Following close on the pul)lic.-ition of the Search Ephemcris 

 bv M. 1.. .Scliulhof, we have the announcement of the re- 

 discovery of Finlay's comet, under conditions which promise 

 to permit of more favourable observations than during its 

 previous apparition in 1886. Perihelion passage is computed 

 to take place on September 7-5, nnd the brightness of the 

 comet on June 18 about twice as bright as when discovered 

 in 1S86, its brilliancy probably steadily increasing up to the 

 end of .\ugust. 



The announcement of its re-discovery at Koenigstuhl was 

 made by telegram, giving the following position ;- 



r, , ''■ S'' 1 <'• h- ■"■ 



lx..\. = 23 3b 3 (igo6. July 16 13 144 Koenigstubl M T.) 



Decl. = — 14 3 (o) I 



The object is travelling in a north-easterly direction, and 

 is described only as bright. 



Report of Observations of Total Solar 

 Eclipse. August 30. 1905. 



The reports of observations made by members of the 

 British Astronomical Association of the total solar eclipse 

 of August 30, 1905, have now been issued together in a 

 most attractive and interesting volume, covering almost all 

 sections of eclipse investigation. The main expedition was 

 stationed at Burgos, under the direction of Mr. C. Thwaites, 

 the duration of totality being about 3ni. 45s. The sun re- 

 mained covered with clouds up to w-ithin 15 seconds of 

 totality, when suddenly a rift appeared, through which the 

 eclipse was observed. The corona was seen of a pearly 

 white colour, not so bright nor with so long streamers as 

 the corona of 1S98. It was, in fact, a typical sun-spot 

 n\aximum corona. Numerous dr.awings of (he corona are 

 given as seen at various stations along the line of totality, 

 iuid a reproduction of a beautiful photograph taken by the 

 Rev. .\. L. Corlie at Vinaroz with a 4-inch objective of 

 t9 ft. 4 ins. focal length, fed with light from a 8-inch 

 coelostat mil ror. 



Especially interesting on account of the meagre spectro- 

 scopic results obtained by the more powerful equipments of 

 the unfortunate expeditions is a reproduction of a very clear 

 spectrogram of the flash spectrum taken by Mr. E. Dickson 

 at Burgos. This was taken with a fixed half-plate camera 



