His experience confirms CD’s view that some species and even some genera of Brachiopoda are consistently more variable than others, and that such variable forms are variable in all localities and at all periods. Similarly a species that shows a lack of variability does so at all points in time and space. Discusses the causes of variability. [See Natural selection, p. 106.]

Sends three tables on the known geological distribution of genera and subgenera of Brachiopoda. Has been continually puzzled by intermediate forms, and is convinced that the greater number of species can be linked together. "Natura non facit saltum."

Many years ago he read a paper to the Royal Scottish Society of Arts on the merits of JH's telescope compared with that of William Parsons (3rd Earl of Rosse); this paper has never been printed. Gives details of his own optical work.

Is grateful for JH's letter and pamphlet. Worked on portraiture before Mr. Baird and assisted him later. Outlines the various lenses he used and made for other people. Is pleased JH has a good opinion of the work of [W. B.?] Rogers. Is he familiar with the works of [Thomas?] Dicks in astronomy?

Has now had ample time in which to study JH's pamphlet. Comments on various points. Has constructed a 4 1/2" aperture achromatic telescope, but the buyer went bankrupt. Would welcome assistance from JH.