132 



NA TURE 



{Dec. 17, 1874 



worked by one central clock movement, each or all being 

 readily thrown out of gear at will. The marking is 

 effected by steel prickers driven by electro-magnets, on 

 the same principle as in the chronograph of the Royal 

 Observatory, Greenwich, though the mechanical details 

 were different. These prickers can also be thrown out of 

 action by a convenient arrangement of resistance coils. 

 The length of a single second of time can, by changing two 

 wheels, be made either one, three-quarters, or half an inch. 

 I had prescribed that the central clock work should be 

 regulated either by the late Leon Foucault's lever 

 governor or by Mr. Siemens' centrifugal fluid governor, 

 but the maker, without consulting me, applied a Watts 

 bail governor with friction-brake, such as is employed for 

 the driving-clock of equatoreals. I did not expect that 

 this comparatively primitive contrivance would secure a 

 sufficiently uniform velocity. But on trial by Capt. 

 Campbell, R.E., and myself, it was found to answer its 

 purpose so well that I am inclined to think a great deal 

 of needless refinement and expense has been wasted on 

 elaborate governors for chronographs. 



Standard Clock. — This is by Messrs. Cooke, of York, 

 and has nothing peculiar in its construction. It has 

 a Graham's dead beat escapement, and a mercurial 

 (metal jar) compensated pendulum, with the contact 

 apparatus necessary for connecting it electrically with 

 the chronograph. 



Three J oiirucymaii Clocks. — These were intended by me 

 to be connected electrically with the Standard Clock, and 

 thus show identical time for each of the principal instru- 

 ments from which the latter might not be visible. I was 

 not satisfied with the mode of driving adopted by the 

 makers, and should have had them altered if time had 

 admitted. Col. Tennant is also dissatisfied with them, 

 but I hope that, with careful adjustment and attention to 

 the batteries and contacts, they may be found effective 

 during the short period of the phenomenon. 



It fortunately happened that whilst these instruments 

 were undergoing examination by me, Capt. W. A. Camp- 

 bell, R.E., of the G. T. Survey of India, who is to assist 

 Col. Tennant v;ith the Venus observations, was in England. 

 The Government, on my application, appointed Capt. 

 Campbell to assist me in testing the instruments, and 

 thus the two objects were gained of securing his valuable 

 experience and skill, and of familiarising him with the 

 instruments which he would have to use. 



I have heard from Col. Tennant of the safe arrival at 

 Roorkee of the photoheliograph, altazimuth, chromograph, 

 and clocks, and of the expected arrival in a few days of 

 the Equatoreal, his last letter to me to that effect being 

 dated 9th Oct., 1874. There would only remain the 

 Transit Instrument, which was much delayed in construc- 

 tion. It was despatched hence on Sept. 18, 1874, and is 

 no doubt now in Col. Tennant's hands. 



In the foregoing statement I have confined myself to 

 those arrangements which I have been personally con- 

 cerned in makmg. But other places in India will be pro- 

 vided with equipments more or less complete for observing 

 the Transit ot Venus — amongst others I may mention 

 Peshawur, Bombay, and probably more than one station 

 in the southern part of the peninsula under the care of 

 Mr. Pogson, Government Astronomer at Madras. The 

 Government of India has thus not been unmindful of the 

 just claims of astronomical science. 



A. Strange, Lieut.-Colonel, 



Inspector of Scientific Instruments 



to the Government of India 



Lambeth Observatory, Nov. 1874 



PRACTICAL SCIENCE AT CAMBRIDGE 

 "p\R. MICHAEL FOSTER, in concluding his course 

 ^-^ of Practical Physiology this term, remarked on the 

 diligence and industry of his class under many difficulties. 



At the beginning of the term he asked their indulgence 

 for the imperfect accommodation he was able to offer 

 them. Thirty students had been entered, and the space 

 available was about sufficient, properly, for ten. Three 

 students had to be placed at each table, instead of one. 

 Several other gentlemen joined the class subsequently, 

 making the class number about thirty-five. Two ladies 

 also attended the lectures, and were provided with a 

 separate place of study. Dr. Foster at his last lecture 

 said that in the previous year the w«it of accommoda- 

 tion had been so keenly felt by himself and class that he 

 was inclined to discontinue his course. He had, how- 

 ever, conducted it through another term, with a larger 

 number of students ; and, as the result, although he ex- 

 pressed pleasure at the work accomplished by his class, 

 he was more than ever inclined to give it up. The pre- 

 sent course would, however, be completed next term ; but 

 he was not able to promise its repetition in the succeeding 

 winter. Want of accommodation militated so greatly 

 against the quality of the work done, and so limited the 

 kind of work that could be attempted, that the benefit 

 seemed almost to be outweighed by the limitations and 

 disheartening accessories. 



The publication of these remarks may serve to draw 

 attention to the general condition of practical science in 

 Cambridge. Chemistrj' and geology are perhaps the 

 subjects for the practical study of which we now have the 

 most reasonable facilities. The Chemical Laboratory has 

 been recently enlarged and improved, and in addition to 

 thi^ ordinary practical courses Prof. Liveing has this term 

 given lectures with practical illustrations in spectroscopic 

 analysis. The lectures have been given during four suc- 

 cessive hours of the afternoon, to four sets of students, 

 the number of students in each class being limited to four 

 or five ; so that thoroughly efficient work could be done. 

 The facilities for study at the Geological Museum have 

 been improved by Prof. Hughes. A typical collection of 

 fossils has been selected and arranged by Mr. Keeping, 

 and provided with catalogues. A typical series of minerals 

 has been arranged and catalogued by IMr. W. E. Koch, 

 B.A., of St. John's College, derived from the ample stores 

 accumulated by the late Prof. Sedgwick. Several large 

 series of rock specimens have been more conveniently 

 arranged for inspection, including those catalogued by 

 the Rev. T. G. Bonney. In addition, advanced students 

 have free access to the many valuable special collections 

 in the Woodvvardian Museum. The Geological Library 

 in the museum has been improved and catalogued ; a 

 valuable section-cutter and an excellent microscope have 

 been purchased, and in other ways the means for the 

 practical study of geology, so far as it can be carried on 

 in a museum, have been greatly improved. 



In Experimental Physics the best conditions for prac- 

 tical study have been secured in the building of the 

 Cavendish Laboratory, in its being furnished with some 

 of the most perfect and valuable physical apparatus in 

 existence, and in the appointment of Prof. Clerk Maxwell 

 and his able demonstrator, Mr. Garnett. No doubt at the 

 earliest possible moment a practical elementary course 

 will be organised, to include those observations which 

 every student of natural science should become familiar 

 with. Sufficient time has not yet elapsed since the com- 

 pletion of the laboratory for the establishment of such an 

 elementary class ; but when it is established a great boon 

 will be conferred on Natural Science students, who, in 

 the study of biology and geology, labour under many 

 difficulties caused by a want of sufficient practical 

 acquaintance with physics. It would be very desirable, 

 also, if some elementary non-mathematical lectures on 

 physics could be given for the benefit of Natural Science 

 students ; such lectures might be given by the Demon- 

 strator, so as not to interfere unduly with Prof. Maxwell's 

 researches and advanced mathematical lectures. It is 

 true that Mr. Trotter gives valuable lectures on physics 



