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



paper of more value than many of the so-called books on surveying 

 that are issued apparently by theorists who form their theories 

 and then attempt to get evidence in favour of them. I shall be 

 delighted to see the paper in print, and most heartily support the 

 vote of thanks. 



The President — I thoroughly endorse the opinions which have 

 been expressed. This paper will be highly esteemed by professional 

 gentlemen. It will be published immediately. We have now 

 made arrangements with our printers to have papers in print a 

 week or two after they are read. 



ON SOME PHOTOGRAPHS OF THE MILKY-WAY, 

 RECENTLY TAKEN AT SYDNEY OBSERVATORY. 



By H. C. Russell, b. a., c. m. g., f. r. s. 



[Read before the Royal Society of N.S.W., August 6, 1890.~] 



The mounting of our photo-telescope being so far complete and 

 waiting only for the object-glass, it became a question whether it 

 could not be turned to some good use, and acting upon a suggestion 

 made by some experiments at the Lick Observatory, I obtained one 

 of Dallmeyer's largest portrait-lenses with a clear aperture of 6 

 inches and focus of 32.6 inches, and determined to take photos with 

 it which should serve to delineate the southern part of the Milky- 

 Way and show the general character, number and grouping of the 

 stars in it. 



Some time was unavoidably lost at the start ; it was found that 

 the visual was outside the actinic focus, and it took a number of 

 experiments to determine where the desired focus was, when 

 determined it was found to be confined to a small space about 5 

 inches in diameter and there is still a doubt in my mind whether 

 any part of the field can be got into sharp focus for stars. It is 

 stated in standard works on photography that in portrait-lenses 

 other considerations are sacrificed to the purpose of getting a good 

 picture of an object 20 or 30 feet distant, and that one of the 

 means used to this end is to separate the lenses more than they 

 should be for distant objects ; this may be so, but after getting an 

 adjustable mounting which permitted various distances between 

 the lenses, I took pictures, gradually reducing the distance at each 

 setting, until the lenses were 2 J inches nearer together than when 



