NATURE 



59 



THURSDAY, MAY 28, 18 



THE AFRICAN ECLIPSE OF \'&T\ 



IT is often said that Science is a thing of slow growth, 

 and it must indeed be confessed that if one turns 

 aside from the advancement of Science as a whole to the 

 advance of any one particular branch of it, the state- 

 ment is too true. Over and over again one gets instances 

 in which crucial experiments suggested by previous work 

 arc separated by decades or even by centuries. One 

 cause to which this slow march is undoubtedly to be 

 attributed is the apathy of men of Science themselves. 

 To any science in which they do not themselves excel, 

 and especially to any newly-opened-up branch of their 

 own technic, the attitude of many men, and especially 

 of official men, of Science, is not merely one of passive 

 resistance ; it is the attitude of the Schoolmen in the 

 time of Galileo over again. We grant that these cramped 

 minds are fortunately in a minority, but the minority is 

 often a powerful one, for the reason, among others, that 

 it is composed of men as a rule advanced in years, far 

 removed therefore from the sympathies, unselfishness, 

 receptivity, and unbounded horizon of youth. 



It is a good sign of the times, therefore, when we find a 



scientific official large-minded enough, and with genius 



enough, to help on with his whole heart new studies as 



well as the old ; and from this point of view we are 



I especially anxious to draw attention to the fact not 



I only that the total eclipse of April 16 of this year has 



I been admirably observed, but that it has been observed 



by the Astronomer Royal of the Cape, Mr. Stone, him- 



1 self, who has thus increased the debt of gratitude which 



' both the mechanical and the physical sides of astronomy 



I owe to him, careless, we doubt not, of the opinion held 



I by a very high authority here in England that the 



I spectroscope — the instrument he employed — is not an 



astronomical, nay, is not even an optical, instrument ! 

 I The line of totality of the eclipse in question struck 

 I land near Port Nolloth, on the west coast of Cape Colony, 

 j somewhere about 250 miles from Cape Town, and passed 

 I over the southern extremity of Africa in a curved line 

 I with the convexity turned towards the north, ending at 

 sunset about half way across. There were three points 

 i whence the totality might be observed : Port Nolloth on 

 ; the coast, O'okiep at the opposite extreme inward, a 

 I hundred miles away ; and Klipfontein, about half way 



i between. The last-mentioned spot was very fortunately 

 the one selected by Mr. Stone. It is known locally as the 

 " Cottage," forming the country or picnicing residence 

 of Mr. Hall, an engineer, and on the brow of a hill rising 

 ' at least some 2,000 ft. above the level of the sea. On the 

 I day of the eclipse down at Port Nolloth there was a cloud 

 ( through which, as at Port Elizabeth and Graham's Town, 

 J the phenomena of the eclipse were all but utterly invisible. 

 \ Up at Klipfontein the weather and the sky were all that 

 J could be desired. 



' Although full particulars of Mr. Stone's observations 

 ' have not been received, the Cape Arj^us of April 25, 

 I a copy of which has been forwarded to us, contains ex- 

 ! tracts from private letters received from Mr. Stone, which 

 ] place us ail couraitt with the main points of the observa- 

 ' tions. The most complete account is as follows : — 

 t Vol. .X.— No. 239 



"I observed the eclipse from Klipfontein. The day 

 vvas most favourable, not a cloud being visible. The 

 sight with the naked eye during the few moments I could 

 spare from my_ work was grand and impressive beyond 

 conception. The eclipse, however, appeared to me to 

 differ a good deal from those lately observed. 



"The rose-coloured flames extended very nearly around 

 the moon, although of course of unequal heights at dif- 

 ferent parts. The corona appeared much less compli- 

 cated. I saw no outlying brushes, and I should without 

 hesitation express an opinion that all the corona I saw 

 was of the same character throughout and belonged to 

 the sun. The less complication of the corona may, how- 

 ever, have been connected with the purity of the atmo- 

 sphere and the absence of clouds. I used a four-inch 

 telescope lent me by Mr. H. Solomon. My spectroscope 

 was one of two dense flint glass of 60". The slit was 

 opened as wide as could allow of a clear sight of Fraun- 

 hofer's lines. This was done to insure my being able to 

 see the spectrum of the corona, which was expected to 

 have been very faint. During the partial eclipse I exa- 

 mined most carefully the spectrum near the moon's limb, 

 and away from the limb, to sec if any fresh lines could be 

 seen near the moon's limb. None appeared, and conse- 

 quently there cannot beany medium capable of producing 

 sensible absorption of light around the moon. As the 

 totality drew near, the portion of the sun's disc uncovered 

 was kept half way across the slit. At the instant of the 

 totality the whole field appeared full of bright lines. I 

 believe that all the principal Fraunhofer lines were re- 

 versed, and seen as bright lines. One of these lines I am 

 certain was the red line B, but no sooner had I begun to 

 count the lines than the spectrum changed into that of 

 hydrogen gas. This spectrum being well known as that of 

 the rose-coloured flames, I did not care to spend the few 

 moments available upon it ; but just glancing at the 

 eclipse to see the brightness of the corona, I turned the 

 telescope upon a bright portion of this beyond the rose- 

 coloured light. The spectrum was much fainter than 

 that of the rose-coloured flames, but there was an ordinary 

 spectrum of some brightness, and across this I feel cer- 

 tain Fraunhofer's lines were still visible, although seen 

 with some difficulty on account of the faintness of the 

 general spectrum. There was also a discontinuous spec- 

 trum near the green of one very bright line, and two very 

 faint lines of less refrangibility. I then turned the tele- 

 scope of the spectroscope over the whole spectrum, from 

 the red to the extreme violet, but I could see no other 

 bright lines than those near the green. My time was 

 now nearly run out, and I turned the telescope again upon 

 the brightest of the lines, and brought the wire of the 

 micrometers to fix its position. The telescope remained un- 

 touched until after the totality, when the micrometer was 

 read and the position of the line referred to the Fraun- 

 hofer's line near it. This bright line appears to agree 

 in position with the one observed by Young. I am satis- 

 fied with the results obtained, considering the instru- 

 mental means at my disposal. I have made magnetical 

 observations at three stations, and hope yet to reach the 

 Orange River for the same object. ]\Ir. Carson and Mr. 

 Hall have been kind to an extent that I could never have 

 expected, and have thrown all manner of facilities in our 

 way." 



It will be seen that the results obtained by Mr. Stone 

 confirm in an importan-; manner several observations 

 made on the ecUpses of 1S69, 1870, and 1S71. The posi- 

 tion of the coronal line 1474 scarcely required confirma- 

 tion, but the two less refrangible coronal lines observed 

 by Pogson in 1S68 have been again seen. The coronal 

 atmosphere was apparently, as might have been expected 

 at this period of minimum sun-spots, smaller than in 

 1 87 1, while the dryness of the air reduced the atmospheric 



