According to Seybold, surveying and navigation were the most popular mathematical subjects taught. Some explanation is to be derived from the statement by Schoen[5] that: "In the days when the 'bounds' of great wilderness tracts were being marked off by deep-cut blazes in the trees along a line, a knowledge of land surveying was a useful skill, and many a boy learned its elements by following the 'boundsgoer' in his work of 'running the line.' And those who did not actually take part in running the line must have attended many a gay springtime 'processioning' when neighbors made a festive occasion out of 'perambulating the bounds'." "Vague land grants and inaccurate surveys," he adds, "made the subject of boundary lines a prime issue in the everyday life of colonial homes." At the same time there was interest in the other aspects of the mathematical sciences. As early as 1743, for instance, a Harvard mathematician named Nathan Prince advertised in Boston that if he were given "suitable Encouragement" he would establish a school to teach "Geography and Astronomy, With the Use of the Globes, and the several kinds of Projecting the Sphere" among other things.[6] A decade later, Theophilus Grew, professor in the academy at Philadelphia which has become the University of Pennsylvania, published a treatise on globes, with the title: _The Description_ and _Use_ of the _Globes_, Celestial and Terrestrial; With Variety for _Examples_ for the Learner's _Exercises_: Intended for the Use of Such Persons as would attain to the Knowledge of those _Instruments_; But Chiefly designed for the _Instruction_ of the young _Gentlemen_ at the _Academy_ in Philadelphia. To which is added Rules for working all the Cases in Plain and Spherical Triangles without a Scheme. By _Theophilus Grew_, Mathematical Professor. Germantown, Printed by Christopher Sower, 1753.[7] Thus, the need for practical mathematical instruments for the surveyor and navigator became critical in proportion to the need for men to make and use them, and it is not surprising to discover that the majority of the instruments produced and advertised by early American makers were for surveying, with nautical instruments in second place. Generally, the surveyors were not professionals; they were farmers, tradesmen, or craftsmen with a sound knowledge of basic arithmetic and occasionally with some advanced study of the subject as taught in the evening schools. The surveying of provincial and intercolonial boundaries required greater skill, however, as well as a knowledge of astronomy, and this work was relegated to the scientific men of the period.