Unpublished letter, 'On the markings of the eelback dun variety of the horse common in Scotland' from W Macdonald to P M [Peter Mark] Roget Macdonald shares his observations on a variety of horse known as the eelback dun, in particular the coloured markings of the horse. He disagrees with conclusions presented in a paper published in volume 111 of Philosophical Transactions by the Earl of Morton [George Douglas], regarding the markings of horses. Subject: Zoology Received 11 June 1839. Communicated by Roget. Whilst the Royal Society declined to publish this paper in full, an abstract of the paper was published in volume 4 of Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London [later Proceedings of the Royal Society] as 'On the markings of the eel-back dun variety of the horse, common in Scotland. In a letter to P. M. Roget, M. D., Sec. R. S. By W. Macdonald, M. D., Fellow of the Royal College of Physicians of Edinburgh, F. R. S. Ed., F. L. S., &c. Communicated by Dr. Roget'. 11 May 1839