110 H. C. RUSSELL. ON SOME PHOTOGRAPHS OF THE 



one, the only way for you to get an idea of its beauty is to examine 

 the picture which I have brought for that purpose and then you will 

 understand the overpowering effect which such a vast multitude of 

 stars, their variations in size and arrangement have upon the mind. 



I began this work, as I have already stated, with the object of 

 delineating the southern portion of the Milky- Way and showing 

 where its limits may fairly be placed, but a host of other questions 

 present themselves as one examines these plates with all the stars 

 of wide sky space brought directly under the eye, in a way that 

 it is otherwise quite impossible to see them : for with a telescope 

 large enough to show these minute stars one is fortunate to get a 

 field of view equal to one-quarter of a square degree, and to carry 

 on such views in the mind's eye, remembering the features of 

 several to compare them as if all seen at once, is impossible. But 

 here we have 140 square degrees at once in view, and we can see 

 how the curve of stars in one telescopic field is but part of an 

 oval, a circle, or some other figure in its full development here ; 

 but I am not going to detain you upon this question. I have not 

 yet had time to examine the plates in detail and read their story, 

 and I must leave these points to a more convenient season. After 

 showing what a large sky space these plates cover (14° x 10°) I 

 shall perhaps be asked why it is necessary to have all the elaborate 

 machinery and large telescopes agreed to at the Paris Conference, 

 and the ten years of work, while with this instrument one man 

 with good weather might do the whole sky in a year. The answer 

 is a simple one : here the object is to get as much into one plate 

 as possible ; there the object is to make the stars as far as 

 possible apart, so that they may be measured accurately, and 

 double stars divided which with this camera are not seen to be 

 doubles at all, and lastly to have all the stars sharply defined. 



One of the most striking features of these star photographs 

 is that some of the well-known dark spaces in the Milky- Way 

 seem to be absent, and one looks in vain for the great rift in the 

 Milky- Way at the head of which stands Alpha Centauri. To the 

 naked eye it is a great dark space dividing the Milky- Way into 

 two streams, and its presence there led to Herschel's speculations 

 of the form of the universe of stars in which we live, and in all 

 other schemes to account for the arrangement of stars in our 

 universe this rift has been an important factor ; and yet as we 

 look at the photograph it cannot be seen, stars as numerous 

 as in other parts round Alpha seem to fill up the void ; and 

 we are driven to accept the conclusion that the theories based 

 upon what the eye sees, are resting upon very faulty data. It is 

 quite evident that the stars extend all over this region as thickly 

 or nearly so as in other parts ; and in future pictures of the 

 -Milky- Way, a very different figure of this and probably of other 



