222 



SCIENCE. 



borderland where matter and force seem to merge into 

 one another, the shadowy realm between the known and 

 the unknown, which for me has always had peculiar 

 temptations. I venture to think that the greatest scien- 

 tific problems of the future will find their solution 'in this 

 borderland, and even beyond ; here, it seems to me, lie 

 ultimate realities, subtle, far-reaching, wonderful." 



GREAT ASTRONOMICAL TELESCOPE. 



The greatest refracting telescope in the world — Lord 

 Rosse's is a reflecting telescope — has been constructed 

 for the Vienna Observatory by Mr. Howard Grubb, at 

 his celebrated manufactory of astronomical instruments, 

 at Rathmines, near Dublin. We give an illustration, 

 from a sepia drawing of it by Mr. G. Browning, and 

 abridge the following account of it from a description re- 

 ceived at this office. 



The idea of crowning the observatory at Vienna with a 

 refracting telescope of surpassing power was conceived 

 by the Austro-Hungarian Government about five years 

 ago. Such a building was worthy of the best instrument 

 that could be constructed. Every visitor to the Austrian 

 capital must be struck by it, standing upon a site of be- 

 tween fourteen and fifteen acres at a height of 200 feet 

 above the city, and extending 330 feet in length and 240 

 feet in width. Desiring to possess the finest telescope 

 which could be procured, the Government commissioned 

 Dr. Edward Weiss, now Director-General of the Observ- 

 atory at Vienna, to visit all the principal observatories 

 and workshops in the world. He. recommended that the 

 task should be confided to Mr. Grubb, of Dublin, 

 who was ordered to construct a refracting telescope of at 

 least 26 inches aperture. A commission was appointed 

 by the Austro-Hungarian Government to superintend 

 the work. It was composed of the following gentlemen : 

 The Earl of Crawford and Balcarres, Dr. Higgins, the 

 Earl of Rosse, Professor Stokes, of Cambridge, Pro- 

 fessor Ball, Astronomer Royal for Ireland, Dr. Stoney, 

 Secretary of the Queen's University in Ireland, many 

 years connected with Lord Rosse's observatory, Dr. E. 

 Reynolds, professor of chemistry, Trinity College, 

 Dublin, and Mr. Walsh, Austro-Hungarian Consul in 

 Dublin. On the 16th ult. the Commissioners reported 

 their unanimous approval of the finished instrument. 



The general form of the telescope is that known as 

 Grubb's modified Gramme, and is similar to the well- 

 known standard equatorial which he constructed for the 

 Earl of Crawford and Balcarres, Dr. Huggins, Oxford 

 University, Berlin, Cork, and other places. It possesses 

 all the modern improvements and special arrangements 

 of an ingenious character, which are rendered desirable 

 by its great size. The length of the tube is 33 feet 6 

 inches, and the aperture is 27 inches. The tube is en- 

 tirely of steel, 2>% feet in diameter in the centre, and 

 tapering to each end. The entire moving parts, includ- 

 ing the tube, polar, and declination axis, counterpoise 

 and various adjustments weigh between six and seven 

 tons ; yet the whole apparatus is under such control that 

 one person can move it about and manipulate it with the 

 utmost ease. The mechanism is remarkable for its 

 solidity and strength, as well as for its exquisite delicacy. 



In order to render the motion of such ponderous instru- 

 ments sufficiently easy, the makers are generally obliged 

 to reduce the diameter of the axes, particularly that 

 known as the declination axis, to an extent that makes one 

 almost alarmed for their safety, to say nothing of their 

 stability. Mr. Grubb, however, has mastered the difficul- 

 ties of the position by a peculiar and most interesting sys- 

 tem of equipoise, by which he is enabled to make his axes 

 so large and solid as to ensure stability and give perfect 

 confidence without sacrificing the ease of motion. The 

 application of antifriction apparatus to the polar axis has 

 been already successfully effected, and was a simple prob- 



lem, but Mr. Grubb has the exclusive merit of applying it 

 to the declination axis, which is a task of great and com- 

 plicated difficulty, demanding the highest scientific skill. 



Another remarkable feature in the work is the ingenious 

 arrangement by which the circle can be read with the ut- 

 most ease and certainty. It is usually a very troublesome 

 operation with large telescopes to read the circle, and 

 when the circles are about 20 feet or more from the 

 ground the labor and delay which it involves are very for- 

 midable. In Mr. Grubb's instrument, the circles are care- 

 fully and accurately divided on a band of gold, and by a 

 system of reflectors, at once beautifully simple and inge- 

 nious, the observer can without stirring from his chair 

 read all the circles of the instruments through one little 

 reader telescope attached to the side of the main tele- 

 scope tube. 



The setting of the telescope is massive and graceful. 

 The frame on which it rests down to the ground level is 

 of cast iron, and there are chambers of considerable size 

 at the base. In the lower one, which is entered by a door 

 at the end, is a clock for driving the instrument in order 

 to follow the paths of the heavenly bodies. The castings 

 of which the frame is formed are of about ten tons weight, 

 and are of simple but not inelegant design. The clock- 

 work is controlled by Mr. Grubb's novel frictional governor, 

 and is also furnished with his new electric control apparatus. 

 There are two right ascension circles, each 2 feet in diam- 

 eter, one read from the eye end of the telescope and the 

 other from the ground floor. The declination circle is 5 

 feet in diameter, and is read from the eye end of the tele- 

 scope. All the circles are divided on an alloy of half 

 pure gold and half pure silver, which is found to be very 

 white and not liable to corrode or tarnish. 



The material for the object glasses was procured from 

 M. Feil, of Paris. The protracted delay in procuring this 

 material for the work was a subject of great anxiety to 

 Mr. Grubb, and occasioned heavy additional outlay on his 

 part. In October, 1879, however, discs were obtained, 

 which in working gave good promise, and in December 

 last he was able to report the work finished — his part of it 

 being, in fact, accomplished in less than half the time 

 stipulated by the agreement with the Austro-Hungarian 

 Government. His task was practically trebled by the 

 difficulty experienced in obtaining pure discs. The suc- 

 cess of his undertaking is regarded with great satisfaction 

 and with national pride. He has supplied equipments to 

 most of the modern observatories, but this telescope is his 

 greatest achievement. 



The AthauFum prints an interesting extract from a letter 

 from Prof. Draper, giving a description of the progress he 

 has made in photographing the nebula in Orion : — " I have 

 succeeded," he says, "in taking stars in it of the 14. 1, 14.2, 

 and 14.7 magnitudes of Pogson's scale. Prof. Pickering 

 has made a series of measures on these magnitudes espec- 

 ially for me at the Harvard College Observatory. You will 

 perceive that we have photographed stars which approach 

 (be minimum visible of my 11 in. telescope, and we may, 

 therefore hope shortly to photograph stars actually too faint 

 to be seen with the eye in the same instrument. The neb- 

 ula, which was exposed 104 minutes, extends over an area 

 of about 15' in diameter, though, as it becomes fainter to- 

 ward the exterior parts, it is difficult to determine its pre- 

 cise limits." This is a great advance ; no star of less than 

 the ninth and a half magnitude has hitherto been photo- 

 graphed. 



A curious magnetic property of the meteoric iron of 

 Santa Cattarina (Brazil), has been lately observed by Pro- 

 fessor Lawrence Smith. Small detached fragments, not 

 weighing moie than 0.1 too.2 gr., were very weakly affected 

 by a magnet ; but on being flattened on a piece of steel, 

 with a steel hammer, thev become very sensitive to it. By 

 heating red-hot, the particles were made to be still more 

 easily attracted than by flattening. The meteoric iron in 

 question contains 66 iron, 34 nickel. 



