The earliest contributions of practical value connected with the subject were made by George Dalgarno, of Aberdeen, in two works, one published in London, 1661, entitled _Ars Signorum, vulgo character universalis et lingua philosophica_, and the other printed at Oxford, 1680, entitled, _Didascalocophus, or the Deaf and Dumb Man's Tutor_. He spent his life in obscurity, and his works, though he was incidentally mentioned by Leibnitz under the name of "M. Dalgarus," passed into oblivion. Yet he undoubtedly was the precursor of Bishop Wilkins in his _Essay toward a Real Character and a Philosophical Language_, published in London, 1668, though indeed the first idea was far older, it having been, as reported by Piso, the wish of Galen that some way might be found out to represent things by such peculiar signs and names as should express their natures. Dalgarno's ideas respecting the education of the dumb were also of the highest value, and though they were too refined and enlightened to be appreciated at the period when he wrote, they probably were used by Dr. Wallis if not by Sicard. Some of his thoughts should be quoted: "As I think the eye to be as docile as the ear; so neither see I any reason but the hand might be made as tractable an organ as the tongue; and as soon brought to form, if not fair, at least legible characters, as the tongue to imitate and echo back articulate sounds." A paragraph prophetic of the late success in educating blind deaf-mutes is as follows: "The soul can exert her powers by the ministry of any of the senses: and, therefore, when she is deprived of her principal secretaries, the eye and the ear, then she must be contented with the service of her lackeys and scullions, the other senses; which are no less true and faithful to their mistress than the eye and the ear; but not so quick for dispatch."
In his division of the modes of "expressing the inward emotions by outward and sensible signs" he relegates to physiology cases "when the internal passions are expressed by such external signs as have a natural connection, by way of cause and effect, with the passion they discover, as laughing, weeping, frowning, &c., and this way of interpretation being common to the brute with man belongs to natural philosophy. And because this goes not far enough to serve the rational soul, therefore, man has invented Sematology." This he divides into Pneumatology, interpretation by sounds conveyed through the ear; Schematology, by figures to the eye, and Haptology, by mutual contact, skin to skin. Schematology is itself divided into Typology or Grammatology, and Cheirology or Dactylology. The latter embraces "the transient motions of the fingers, which of all other ways of interpretation comes nearest to that of the tongue."