August ii, 1910] 



NATURE 



manipulation, as compared with the lined screen, appear 

 to have hindered its adoption in those cases where it offers 

 especial advantages, Messrs. Penrose and Co., of log 

 Farringdon Road, have just issued a booklet of instruc- 

 tions for its use. The pamphlet includes specimens of each 

 of the ten degrees of fineness, suitable for work from large 

 posters to the finest photogravure. The impressions show 

 what fine results the screen yields, the chief peculiarity 

 being the entire absence of the regular grain that some 

 persons find so objectionable in the usual type of photo- 

 block. 



The report of the senior analyst, Cape of Good Hopr' 

 Government Laboratories, for the year 1909, contains some 

 interesting reading. About three-fourths of the samples 

 examined (3154 out of 3820) consisted of foodstuffs, 

 beverages, and drugs ; these call for no special comment 

 except, perhaps, to question the utility of giving much 

 analytical detail in a publication of this kind. The re- 

 mainder of the samples reflect the chai'acter of the country : 

 they are mainly mineral, agricultural, and toxicological 

 articles. Gold assays are the most numerous amongst the 

 mineral analyses, which include also the testing of coals, 

 supposed platiniferous rocks, copper, iron, manganese, and 

 tin ores, and supposed diamonds. Amongst the toxico- 

 logical cases, one is especially noteworthy. A native 

 woman had been poisoned with an indigenous bulb 

 administered by a Kaffir " doctor," and it took four months 

 to obtain proof that such bulbs (Heemanthus) could pro- 

 duce the fatal effects in question. This delay was due to 

 lack of knowledge concerning the local poisons, and the 

 senior analyst urges that a research into the properties of 

 the vegetable drugs and poisons of South .'\frica should be 

 carried out systematically. At present, any such investiga- 

 tions are merely casual and incidental upon legal proceed- 

 ings. The production of barley suitable for brewing 

 purposes, and an investigation into the agricultural soils 

 of the colony, are some of the other topics mentioned in 

 a report which everywhere bears evidence of useful activity. 



We learn from the Engineer for August 5 that the first 

 of the large caissons for the new foundations of the Quebec 

 Bridge was launched at the works yard, near the bridge 

 site, on July S. This particular caisson is for the new 

 north pier, and will be situated clear of the old pier, 

 its centre being 57 feet further out from the shore. The 

 new centre line of the bridge has been decided upon 

 15 feet west, or upstream, from the old centre, this altera- 

 tion enabling the new superstructure to be 30 feet wider 

 than the old. The new south pier will be 15 feet nearer 

 the river centre, consequently the span will be 1758 feet 

 instead of 1800 feet, as before. The rebuilding of the 

 south pier presents many more difficulties than the north. 

 The new south pier will occupy very nearly the site of 

 the old, necessitating the placing of a caisson at the side 

 of the existing one, and another across the end of the 

 pair. Upon the three a new caisson, 79 feet by 180 feet, 

 will be sunk. It is thought that the latter will be the 

 largest ever constructed for this class of work. 



\ DESCRIPTION of the hydroplane Miranda IV., built by 

 Sir John Thornycroft, appears in Engineering for August 5. 

 This boat is 26 feet long by 6 feet beam, and 2 feet 6 inches 

 deep. In general outline she approaches very much to 

 the shape of an ordinary boat, but the bottom is specially 

 adapted to make her skini at high speeds. This arrange- 

 ment gets over the difficulties of the original type of hydro- 

 plane, for at moderate speeds she goes through the water 

 in a similar manner to an ordinary boat, and the variation 

 of form necessary to make her skim is so small as not 



materially to affect her performance. When skimming, a 

 small portion of the length amidships carries the weight, 

 the rest of the boat being entirely clear of the water with 

 the exception of a small length aft, which may have 

 enough weight on it to make the boat stable longitudinally. 

 The greater part of the bottom being thus clear of the 

 water, frictional and other resistances are very greatly 

 reduced. It is remarkable how small the disturbance of 

 the water is considering the speed of the boat, which has 

 exceeded 31 knots under somewhat unfavourable condi- 

 tions. If the speed development of hydroplanes is found 

 to follow the same law as that of torpedo boats, a hydro- 

 plane 52 feet long, 10 tons displacement, with a brake- 

 horse-power of 950, should do 45 knots, and a speed of 

 60 knots might be obtained from a boat 110 feet long. 

 Such development depends on the progress made with 

 petrol motors of large power, and in a matter of this 

 kind it is not wise to be in too great a hurry. 



Mr. Werner Laurie will publish shortly " The Black 

 Bear," by Mr. W. H. Wright, author of " The Grizzly 

 Bear." 



Messrs. D. Appleton and Comr^ny are publishing 

 immediately a new work entitled " Up the Orinoco and 

 down the Magdalena," in which Mr. H. J. Mozans relates 

 his travels to South American countries and across the 

 Andes. 



NO. 2128, VOL. 84] 



OUR ASTRONOMICAL COLUMN. 



Photographs of Nebula. — Among the recent additions 

 to the Royal Astronomical Society's collection of celestial 

 objects are three of surpassing excellence taken by Dr. 

 Ritchey with the new 60-inch reflector at Mount Wilson. 

 The objects are the spiral nebulse M. 51, M. Si, and M. loi, 

 and these photographs bring out remarkable details as to 

 their structure; the spirals of M. loi are shown as broken 

 up into soft, star-like condensations, like nebulous stars. 



Dr. Ritchey has made a number of important improve- 

 ments to his camera, and now uses two guiding eye-pieces^ 

 one on each side of the centre, in order to allow for any 

 possible slight rotation of the field ; a power of 800 is 

 employed in the eye-piece. By using a smaller plate, only 

 33 inches square, the guiding star comes much nearer the 

 centre of the field, that is, nearer the object under observa- 

 tion. He also has the plate carrier easily detachable, so 

 that it may be taken off, and accurately replaced, every 

 half-hour or so, to allow of re-focussing ; this is done by 

 using a knife-edge in the focal plane, and by such fre- 

 quent re-focussing he keeps in the true focal plane within 

 I or ij thousandths of an inch. With an exposure of 

 7-5 hours, the photograph of M. loi shows practically 

 perfect star images, of which the smallest are only i-b 

 seconds of arc in diameter, and Dr. Ritchey states that 

 an e.xposure of 3I hours on the globular cluster M. 3 shows 

 tens of thousands of star images which are only 1-15 

 seconds in diameter. 



Photographs of parts of the Great .Andromeda nebula, 

 the Ring nebula in Lyra, and the Crab nebula were also 

 sent, and are strikingly beautiful ; much new light is 

 likely to be thrown on the structure of these objects from 

 the careful study of the negatives. A preliminary study 

 shows that while in some (e.g. M. loi) the spirals are 

 broken up into "nebulous stars," in others <e.g. M. 64, 

 Comae Berenices) they are apparently smooth ; in M. 101 

 more than 1000 of these condensations have been counted. 

 In the Andromeda nebula the central parts are apparently 

 regular, with complicated dark rifts, and the spiral 

 extends practically to the nucleus, but the outer branches 

 contain great numbers of the " nebulous stars " (Monthly 

 Notices R.A.S., vol. Ixx., No. 8). 



Halley's Comet. — The Journal of the Royal Astro- 

 nomical Society of Canada (vol. iv. , No. 3) contains re- 

 productions of fifteen photographs of Halley's comet, taken 

 at the Dominion Observatory, Ottawa, by Mr. Motherwell, 

 during' the period May 3 to June 9, also reproductions 

 from two photographs taken by Prof. Barnard, at Yerkes, 



