The Eclipse Expedition at Viziadurg ¹

Abstract

II. WITH regard to securing the best possible observations along all lines, the perfect organisation of time signals was of the first importance; indeed, a fundamental condition for success. The headquarter staff, under Captain Batten, was stationed at the eclipse clock, about which a word must be said. In an eclipse, especially when there are as many observers as we had on this occasion, it is well that every one shall know that he will get a good square look at it some time or other. In early eclipse work this was not recognised, and I never felt more annoyed in my life than, when I was in India, in 1871, I found that in consequence of my ignorance of eclipse organisation, Captain Bailey, of the Royal Engineers, who travelled 400 miles to our camp to help us, did not see the eclipse at all. He volunteered to give us the time, and took to rehearsing the work daily. I said to him, “What you have to do is to put your chronometer on the table and then sit down facing the sun, so that at any time you like during the eclipse you can look off the face of the chronometer and see the eclipse; because now you have come so far it won't do for you to go away without seeing anything.” He said, “Well, I have been practising for the last two days, and I find it very difficult.” I said, “What are you going to do about it?” He replied, “Well, I shall go on practising it till I do it.” But to my horror, just before the eclipse began, I saw him take his chair to the other side of the table, deliberately place his back to the sun and look at the chronometer, and he never saw the eclipse at all. I was determined that that should never happen again in any eclipse that I had anything to do with, and since then I have always doubled the timekeepers, and given one-half of the eclipse to one timekeeper, and the other half to another. The “eclipse clock” is of rather, peculiar construction. It only possesses a seconds-hand controlled by a seconds-pendulum. The face of the clock shows seconds, and a spiral on which the times are marked, so that there can be absolutely no mistake made as to the time. Not only can the even seconds be given in that way, but if a signal at any particular time is requisite for any particular operation in any of the observatories, the time signalman can give that time as well, so that all the operations are kept perfectly steady. The pendulum (and therefore the clock) is started by cutting a thread at the word “go,” which means the beginning of the eclipse. Then one of the timekeepers turns his back to the sun, stands in front of the clock, and reads out the time-signals “120 seconds left,” and so on, which are marked along the spiral, as the hand reaches them, while the other is looking at the eclipse. The half-time signal (“60 seconds” on this occasion) is sung out by both, and then they rightabout face, one man going off duty and the other talcing it up. In that way both see the eclipse. In order to give an idea of the importance of keeping the time during an eclipse, I will give our eclipse time table.