Three instruments signed by Bowles have survived, and all show signs of considerable wear. They are surveying compasses made of walnut, having maple sighting bars and a silvered brass vernier set under the glass. Two examples, one in the Streeter Collection of Weights and Measures at Yale University and one owned by this writer are almost identical in size, form, and details. The only variation is that the Yale example (fig. 67) has a bubble level under a brass strip set into one end, an item lacking in the other example (fig. 68). The compass card, made from a line engraving, is identical in each of the three examples. A floriated fleur-de-lis on the North point has a compass and square at its base, and the name T. S. BOWLES is on a riband over it. Adorning the East point is an American eagle bearing a shield with stars and stripes and clutching arrows in one claw and a laurel twig in the other. In a ring within the central medallion is inscribed (see fig. 68), "* T. S. BOWLES * PORTSMOUTH, N.H. *" [Illustration: Figure 67.--Wooden surveying compass made by Thomas Salter Bowles of Portsmouth, New Hampshire. With spirit level. Made of birch, the compass is 13 in. long and has a diameter of 6 in. In the Streeter Collection of Weights and Measures, Yale University.] The most interesting of the three instruments was acquired by the Dartmouth Museum as part of a collection of the late Frank C. Churchill, an inspector in the Indian Service. The instrument (fig. 69) is a quarter circle with a compass in its center and sighting bars mounted on a swinging arm that reads the angle of the brass scale on the arc by means of a vernier. It is mounted on a wooden tripod with the customary ball-and-socket joint, which permits it to be placed on a vertical plane. A built-in plumb bob at the side helps to establish the vertical.[127] Interesting features of this instrument are two inscriptions engraved on the brass strip on the top of the dial. One states that it was "INVENTED BY P. MERRILL ESQ." and the other relates that it was "MADE BY JOHN KENNARD NEWMARKET." No information about P. Merrill has been found, and it is presumed that it was he who conceived the idea of combining the various elements into a single instrument and that it was made under his direction by Kennard. [Illustration: Figure 68.--Wooden surveying compass made by Thomas Salter Bowles (1765/70-post 1821) of Portsmouth, New Hampshire. Made of walnut, it is 12 in. long and has a diameter of 5-3/8 in. With walnut sighting bars. In collection of writer.] [Illustration] [Illustration: Figure 69.--Wooden surveying instrument inscribed "Invented by P. Merrill, Esq." and "Made by John Kennard, Newmarket." Made of walnut, 7-3/4 in. long; in its original pine case, with cover. The compass card and dial (see opposite) were made by Thomas Salter Bowles of Portsmouth. In Frank C. Churchill Collection, Dartmouth College Museum, Hanover, New Hampshire.]