Asks TD about variation among brachiopods.
Asks TD about variation among brachiopods.
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.]
Asks TD to carry out research on brachiopods to see whether the forms in one formation are intermediate between those above and below.
Describes unpublished study of spirifers by J. W. Salter.
Thanks TD for his letter. Difficulties with CD’s theory are many and great, but CD thinks the reason is that we underestimate our ignorance. The imperfection of the geological record counts heavily for CD. His greatest trouble is weighing "the direct effects … of changed conditions of life without any selection, with the action of selection on mere accidental (so to speak) variability. I oscillate much on this head, but generally return to my belief that the direct [effects] … have not been great."
Is surprised that any one, like W. B. Carpenter, can go as far as to believe all birds may have descended from one parent, but will not go further and include all the members of the same great division. Such beliefs make "Divine mockeries" of morphology and embryology, the most important of all subjects.
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."
Thanks TD for catalogue of his Cretacean fossils.
Regrets he cannot visit Brighton.
No summary available.
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.
Outlines the differences between the telescope of his own father and that of Lord Oxmantown [William Parsons]. Comments on various lenses. Sends him a little work of his own on telescopes.
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.