40J 



NA TURE 



{March 23, 1876 



Dr. Werner Siemens has constructed a selenium pho- 

 tometer, in which the selenium is prepared so as not to be 

 affected by the changes to which that substance is liable, 

 and which consists of a single sensitive plate mounted 

 upon a vertical axis, upon which it can be turned through 

 a certain angular distance limited by stops. When touch- 

 ing the one stop the selenium stands opposite the normal 

 candle, and when touching the other opposite the light to 

 be measured, the distance upon the former being changed 

 upon a scale until no effect upon the needle of a galvano- 

 meter is produced in turning the sensitive plate in rapid 

 succession from the one stop to the other. 



The lecture was concluded by the exhibition of a sele- 

 nium eye, which Mr. Siemens had prepared to illustrate 

 the extraordinary sensitiveness of the selenium prepara- 

 tions. It consists of a hollow ball with two circular 

 openings opposite each other, the one being furnished 

 with a lens i^ inches in diameter, and the other with an 

 adjustable stopper carrying a sensitive plate, which is 

 connected by wires to a galvanometer and one Daniell's 

 cell. The lens is covered by two slides representing eye- 

 lids, the ball itself being the body of the eye, and the 

 sensitive plate occupying the place of the retina. Having 

 placed a white illuminated screen in front of the artificial 

 eye, on opening the eyelids a strong deflection of the 

 galvanometer was observed, a black screen giving hardly 

 any deflection, a blue one a greater, a red a much greater, 

 but still short of that produced by the reflected white 

 light. The eye was thus sensitive to light and colour, and 

 as stated, it would not be difificult to arrange a contact 

 and electro-magnet in connection with the galvanometer, 

 so that intense light would cause the automatic closing 

 of the eyelids. The artificial eye is subject to fatigue, 

 and the lecturer considered that this experiment might 

 be suggestive to physiologists as regards the natural con- 

 joint action of the retina and the brain. 



THE LATE COLONEL STRANGE, F.R.S. 



T lEUT.-COL. ALEXANDER STRANGE, F.R.S, 

 •*— ' whose death we last week announced, was the fourth 

 son of the late Sir Thomas Strange, and was born at 

 Westminster on the 27th of April, 1818, and was educated 

 at Harrow. On leaving school in 1834, at the early age 

 of sixteen, he proceeded to India, and joined the 7th 

 Regiment of Madras Light Cavalry, where his natural 

 talents began to develop themselves. He shortly after- 

 wards made the friendship of General Worster, who soon 

 discovered that he had mechanical abilities of the highest 

 order, and who subsequently instructed him in the use 

 of astronomical and surveying instruments, and pointed 

 out to him that nature had intended him for a scientific 

 career. During the next few years he became a devoted 

 student at the Magnetic and Meteorological Observatory 

 at Simla, then under the direction of Major-General 

 Boileau, R.E., at whose recommendation he was nomi- 

 nated, in 1847, by Col. (now Sir Andrew) Waugh, R.E., 

 Surveyor- General of India, to the office of Second Assist- 

 ant in the Great Trigonometrical Survey, where he found 

 work suited to his talents. He was originally selected on 

 account of his ability as an observer, and for his extra- 

 ordinary mechanical skill, which in this department was 

 of special value, and was dii?played in such a remarkable 

 degree as to call forth rue highest commendation from 

 Col. Waugh. In the season 1848-49 he was attached to 

 the party under Capt. (now Col.) Renny Tailyour, R,E., 

 in order that he might acquire a practical knowledge of 

 geodetical operations. Such was the rapidity with which 

 he made himself master of this difficult subject, that in 

 1850 he was promoted to the grade of First Assistant. 

 Capt. Tailyour was ordered to undertake the triangu- 

 lation of what is known as the " Karachi Longitu- 

 dinal Series," which constitutes the southern flank 

 of that considerable portion of the principal tri- 



angulation of the Survey of India known as the 

 North-west Quadrilateral. It commences at Sironj in 

 Central India, and terminates at Kardchi, in Sind. The 

 extent of this arc of longitude is equivalent to 670 miles 

 in length, covers an area of 23,000 square miles, and is 

 one of the largest longitudinal arcs ever measured on 

 the surface of the globe. At the end of the first season, 

 Capt. Tailyour's services being required at head-quarters, 

 Capt. Strange was ordered to take over the entire charge 

 of the Series, and it is on this great undertaking that his 

 fame as an Indian Surveyor rests. After [crossing the 

 Desert, over which the triangulation had to be carried 

 nearly 200 miles, the work was carried on with the highest 

 skill across the Plains of Sind, until at length, after much 

 anxiety, and having overcome almost insuperable diffi- 

 culties, the last angle which completed this great triangu- 

 lation was measured on April 22, 1853, and the work 

 brought to a successful close. 



The remarkable energy and rapidity with which this 

 series was carried on, imder many and great difficulties, 

 was reported by the Surveyor-General to reflect on him 

 the highest credit. He was directed to join the Surveyor- 

 General's camp near Attock, where he took part in the 

 verificatory base line. After this he returned to Kardchi 

 with the base-line apparatus, and took a leading share 

 in the measurement of the base-line at that place in 

 the year following. Meantime he had been distin- 

 guished with the title of " Astronomical Assistant." 

 In 1855 Strange joined the Surveyor-General's Head 

 Quarters' Office, and in the following year was placed 

 in charge of the triangulation which was being extended 

 from Calcutta southwards towards Madras, along the 

 eastern coast. In April, 1857, whilst conducting the 

 triangulation in the Goomsoor Hills, a notoriously un- 

 healthy tract, he was struck down by jungle fever, and 

 was .afterwards ordered to the Neilgherry Hills for the 

 recovery of his health. In the year 1859 he was pro- 

 moted to the rank of major, and in accordance with the 

 then existing regulations of the service retired from the 

 Survey, on which occasion he received the special thanks 

 of the Government of India. 



In January, 1861, he returned to England after twenty- 

 six years' continuous service in India, and finally retired P 

 from the army as lieutenant-colonel on the 31st of De- 9 

 cember, 1861. His career in England was no less bril- 

 liant than that in India. In 186 1 he was elected a Fellow 

 of the Royal Geographical Society as well as a Fellow of 

 the Royal Astronomical Society. He served on the 

 Council of the latter from 1863 to 1867, and was Foreign 

 Secretary from 1868 to 1873. On the 2nd of June, 1864, 

 he was elected a Fellow of the Royal Society, of which 

 he soon became a distinguished member ; he served on 

 the Council from 1 867 to 1 869. 



In the year 1862 the Secretary of State for India in 

 Council sanctioned the provision of an extensive equip- 

 ment of geodetical and astronomical instruments of the j 

 first order, for the service of the Great Trigonometrical j 

 Survey of India, consisting of one great theodolite, two 

 zenith sectors, two 5-feet transit instruments, two electro 

 chronographs, two diagonal transit instruments, two 

 12-inch vertical circles, and three astronomical clocks. 

 The task of designing and superintending their construc- 

 tion was entrusted to Lieut.-Col. Strange, who was also 

 appointed to the post of Inspector of Scientific Instru- 

 ments to the Indian Government. To enable him to test 

 these valuable instruments as well as the current supply 

 required by the Public Works, Survey, Meteorological, 

 and various other Departments in India, an Observatory 

 was estabhshed at the India Store Depot in Lambeth 

 from designs prepared by himself. This observatory, in 

 its various ingenious details, is a monument of Col. 

 Strange's consummate mechanical genius. 



At this Observatory, theodolites, levelling instruments, 

 prismatic compasses, sextants, telescopes, barometers, 



