March 30th, 1875.
Dear Sir,—You have asked me for my opinion of the 10-inch speculum. I have tested it, and can speak in the highest terms of its performance. Definition in good air is as near perfection as it is possible to imagine. Such tests as ζ Cancri, γ2 Andromedæ are well divided. The 6th star in the trapezium stands out well clear of its brighter neighbour. On the moon any power may be applied, only lessening the light, but retaining sharpness of outline. I have tried a good many telescopes, but never yet saw these 10-inch mirrors surpassed. The image of a star disc expanded on each side of the focus is of as nearly the same appearance as possible.
Yours truly, W. P. Matthews.
416, Brixton Road,
April 20th, 1875.
Dear Sir,—In compliance with your request, I send particulars of my observation on φ Draconis. It was about 12.45 this morning when I directed my 8-1/2-inch to this object, the air was very unsteady, in fact not nearly so good as some nights lately, and I well divided it with a power of 450. I then used a 6-1/2-inch stop, which I found very much increased the steadiness of definition.
Yours very respectfully, P. H.
10th July, 1874.