OcL 14, 1875J 



NATURE 



517 



berg. Prof. Schlegel at first identified them with the 

 Mooruk, but afterwards admitted their distinctness. My 

 behef is that they are probably the same as the next 

 species (C wesfermanm), although the colours of the 

 neck, as restored in the stuffed specimens, do not quite 

 agree. 



7. Westerman'S cassowary (C westermaHnt).~Th\s 

 species I established on a bird still living in the Zoological 

 Gardens, which we received from Mr. Westerman in 1871. 

 At first I referred this bird to C. kaupi, of Rosenberg, 

 until that naturalist showed that the pretended species 

 which he had so named was nothing more than the young 

 of C. uniappendiculatiis. I then changed our bird's name 

 to C. ivcsiermanni. I have recently seen two other living 

 specimens of this bird in the Zoological Gardens at 

 Rotterdam. It has been suggested that its true home is 

 the island of Jobie, in the Bay of Geelvink, where Dr. 

 Meyer ascertained the existence of a Cassowary, but was 

 not able to procure specimens. 



8. The Painted-necked Caszowkkv {C. picticolUs). 

 — This species was likewise established by me on a speci- 

 men now living in the Zoological Gardens, which was 

 obtained by the officers of H.M.S. Basilisk at Discovery 

 Bay, on the east coast of New Guinea. It greatly resembles 

 the Mooruk, but differs in its brilliantly-coloured neck, of 

 which I have given a drawing in the P. Z. S. for the 

 present year (1875, Part I.) 



9. The Mooruk, or Bennett's Cassowary (C. ben- 

 iietti). — In 1857 Mr, Gould described this Cassowary from 

 a drawing sent to him by Dr. George Bennett, of Sydney, 

 and soon afterwards a living pair were sent to us by our 

 excellent friend, after whom the species had been named. 

 These birds bred in the Gardens in 1864, but we have 

 now unfortunately lost them. Bennett's Cassowary is an 

 inhabitant of New Britain, to the east of New Guinea, 

 and is easily distinguishable from its congeners by its blue 

 throat and back of the neck. 



Omitting for the moment the doubtful C. ^apuanus, it 

 will be thus seen that we have tolerably certain indica- 

 tions of the districts in which the other eight Cassowaries 

 are found. It would be very desirable, however, to get 

 further information concerning them, and also to ascer- 

 tain what is the Cassowary of Jobie, and whether the 

 other islands adjacent to New Britain possess, as is 

 probable, indigenous species of this group. 



P. L. Sclater 



ANOTHER MONSTER REFRACTOR 



THE experiment rendered possible, now some ten 

 years ago, by Mr. Newall, and made with such 

 triumphant success by Mr. Cooke, is again bearing fruit. 

 Another monster telescope, indeed the largest yet at- 

 tempted, is now in course of construction at Mr. Grubb's 

 new works, near Dublin. This instrument has been 

 ordered by the Imperial and Royal Austro- Hungarian 

 Government for the new Observatory now in course of 

 erection at Vienna. The object-glass will have an aper- 

 ture of over 26 inches, probably about 27 inches, according 

 as the discs of glass, which are being manufactured in the 

 rough, by M. Feil, of Paris, may turn out on finishing. 

 The focal length is to be about 32 feet. The general form 

 of mounting will be modified to suit the special require- 

 ments of such a monster instrument. The great base 

 casting (weighing some seven to eight tons) will form a 

 chamber (about 12 feet long, 4 feet 6 inches wide, and 8 

 feet high) for the clock, which will be massive in propor- 

 tion to the other parts. The axes will all have their fric- 

 tion relieved by anti-friction apparatus. The tube will be 

 entirely of steel, and all the various motions of the instru- 

 ment, as well as the reading of the different cir jles, will 

 be available to the observer from the eye-end of the 

 telescope. 



A circular chamber of 45 feet diameter has been pro- 

 vided in Mr, Grubb's new workshops, to be covered for 



the present by a corrugated iron roof 50 feet high. In 

 this the telescope is to be set up, and over this will be 

 meanwhile erected an enormous steel dome, revolving on 

 the system of rollers designed some years since by Mr. 

 Thomas Grubb, and adopted at Dunsink Observatory, 

 near Dublin, and at Lord Lindsay's Observatory. All of 

 this dome and revolving machinery is afterwards to be 

 removed to Vienna. Thus, by taking do\Vn the stationary 

 iron roof, when the steel dome is erected over it, the equa- 

 torial will be placed in perfect working order, under its 

 own roof in Dublin, for trial. It is proposed to attempt to 

 illuminate the verniers and circles by Geissler's tubes. If 

 M. Feil can, as he hopes, perfect the pair of discs required 

 within twelve months, Mr. Grubb expects to have the whole 

 instrument complete by the autumn of 1878, in which 

 year, we may remark, it is not impossible that the British 

 Association may be invited to Dublin. Should Lord 

 Rosse's reflector be in order and the Vienna telescope 

 complete. Section A will certainly muster in great force. 



THE DIFFERENCE OF THERMAL ENERGY 

 TRANSMITTED TO THE EARTH BY RADIA- 

 TION FROM DIFFERENT PARTS OF THE 

 SOLAR SURFACE 



DERE SECCIII, in the second edition of "Le Soleil," pub- 

 _ lished at Paris 1875, again calls attention to the result of 

 his early investigations of the force of radiation emanating from 

 different regions of the sun's surface, reiterating without modifi- 

 cation his former opinions regarding the absorption of the radiant 

 heat by the solar atmosphere. It will be well to bear in mind 

 that the plan adopted by the ItaHan physicist in his original 

 researches, on whicli his present opinion is based, was that of 

 projecting the sun's image on a screen, and then, by means of 

 thermopiles, measuring the temperature at different points. The. 

 serious defects inseparable from this method of measuring the 

 intensity of the radiant heat I need not point out, nor will it be 

 necessary to urge that a correct determination of the energy 

 transmitted calls for direct observation of the temperature pro- 

 duced by the rays projected towards the earth. Accordingly, 

 on taking up that branch of my investigations of radiant heat 

 which relates to the difference of intensity transmitted from diffe- 

 rent parts of the sun's surface, I adopted the method of direct 

 observation. The progress was slow at the beginning, owing to 

 the necessity of constructing an astronomical apparatus of unusual 

 dimensions, but having devised means which rendered the em- 

 ployment of any desirable focal length practicable, the work has 

 progressed rapidly. An instrument of 177 metres (58 feet) focal 

 length, erected to conduct preliminary experiments, has proved 

 so satisfactory that the construction of one of 30 metres focal 

 length, which I supposed to be necessary, has been dispensed 

 with. Considering that the apparent diameter of the sun at a 

 distance of 177 metres from the observer's eye is 162*4 

 millimetres even when the earth is in aphelion, the efficacy of 

 the instrument employed might have been anticipated. The 

 nature of the device will be readily comprehended by the follow- 

 ing explanation: — Suppose a telescopic tube 17' 7 metres long, 

 I metre in diameter, devoid of object-glass and lenses, and 

 mounted equatorially, to be closed at both ends by metallic plates 

 or diaphragms, at right angles to the telescopic axis. Suppose 

 the diaphragm at the upper end to be perforated with two circu- 

 lar apertures 200 millimetres in diameter, situated one above 

 the other in the vertical line, 360 millimetres from centre to 

 centre ; and suppose a third circular perforation whose area is 

 one-fifth of the apparent area of the solar disc, viz. 72 "6 milli- 

 metres diameter, to be made on either side of the vertical line. 

 Suppose, lastly, that the diaphragm which closes the lower end 

 of the tube be perforated with three small apertures 6 milli- 

 metres in diameter, whose centres correspond exactly with the 

 centres of the three large perforations in the upper diaphragm. 

 The tube being then directed towards the sun, and actinomcters 

 applied below the three small apertures in the lower diaphragm, 

 it wi 1 be evident that two of these instruments will, after due 

 exposure to a clear sun, indicate maximum solar intensity, say 

 35° C, while the actinomcter applied in line with the perforation 

 whose area is onc-fifth of the apparent area of the solar disc, 



will indicate •— = 7° C, unless the central portion of the solar 



