Perseverance Island; Or, The Robinson Crusoe of the Nineteenth Century

by Douglas Frazar

	Day. Hour. Min.
Moon enters penumbra	30 5 44 A.M.
Moon enters shadow	30 6 53 "
Total phase begins	30 8 49 "
Total phase ends	30 9 39 "
Moon leaves shadow	30 10 45 "
Moon leaves penumbra	30 11 55 "

This was all I needed to verify my longitude past peradventure, and I went to work at once, calculating when the eclipse ought to take place, nearly, with me.

At a rough calculation I knew that my island was situated somewhere between the 110° and 120° of longitude west of Greenwich, that is to say, in the neighborhood of seven hours' difference of time later than Greenwich time. Therefore I knew that if the moon entered the penumbra at Greenwich (although invisible) on the 30d. 5h. 44 min. A.M. that I ought to look for it to occur visibly to my eyes somewhere from one to two o'clock in the afternoon of the same day, or seven hours later. The exact difference in the time between Greenwich and that to be observed on my island, changed into degrees and minutes, would, of course be the true longitude west of Greenwich.

It was with the utmost anxiety that I awaited the coming of the 30th of September, for it all depended upon pleasant weather whether or not I should be able to make my observation. I placed my astrolabe so as to be able to move it quickly in any needed direction, as I intended to use the tube to look at the sun through so as not to blind my eyes. I also prepared my birch bark in the house, and commenced practising myself in counting seconds, for I should have to leave my instrument and go to the house, counting all the time to note the time marked by my clock. I found upon practice that I could not make this work very successfully, and that according to the state of my feelings or excitement I counted long and short minutes. This would not do; I must invent something better; and I finally bethought myself of counting the beatings of my pulse with the finger of one hand upon the wrist of the other, and applying the proportion to the interval between the observed time by my clock.

The morning at last came that I so much desired, and nothing could be more beautiful than the balmy, spring-like day that surrounded me. The sky was cloudless and the sun shone down in splendor through a clear and pure atmosphere. The morning passed slowly away, and it seemed as if the moon and sun would never approach each other; but finally, in the afternoon, the heavens showed me that the eclipse would soon take place, and I made my arrangements to take four observations, as follows: Time when moon entered shadow; time when total phase began; time when total phase ended; time when moon left shadow.

Nothing could have been better than the afternoon I experienced to make these observations, and in less than six hours the whole affair was over, with the following result, I having carefully regulated my clock as near as possible by an observation at noon:—

	Day.	Hour.	Min.
Moon enters shadow at island (civil account)	30	2	50 P.M.
Moon enters shadow at Greenwich	30	6	53 A.M.
Difference		7	57
Total phase begins at island	30	4	48 P.M.
Total phase begins at Greenwich	30	8	49 A.M.
Difference		7	59
Total phase ends at island	30	5	34 P.M.
Total phase ends at Greenwich	30	9	39 A.M.
Difference		7	55
Moon leaves shadow at island	30	6	41 P.M.
Moon leaves shadow at Greenwich	30	10	45 A.M.
Difference		7	56
		Hours.	Min.
Sum of differences, four observations		31	47
	Hours.	Min.	Sec.
Mean of same	7	56	45

Which, reduced to time, gives the longitude of the island 119° 11′ 15″ west of Greenwich.

There, my problem was done and I was for the moment happy. Perhaps some will wonder why I cared to obtain the latitude and longitude of my island at all. Let me explain. My Bowditch's Epitome gave the latitude and longitude of all prominent capes, harbors, headlands, light-houses, etc., in the whole Pacific Ocean. In other words, knowing now the latitude and longitude of my own island, I had only to project a chart on Mercator's projection, pricking off the relative positions of the land on all sides of me, as well as the position of my island, to have a practical and useful chart. Of course I should not be able to draw the coast line or the circumference of any island, but my chart would show just what latitude and longitude Easter Island was in, for instance, and just how far and in exactly what direction my island lay from it. Also, how far I was from the American coast, and the exact distance and course from any of the principal ports such as Lima, Valparaiso, Pisco, etc. How far from New Zealand and the Society Islands, and in what direction from them.