VOL. LIII.] PHILOSOPHICAL TRANSACTIONS. 701 



yet not absolutely true, because they ought to flow with a uniform and unin- 

 terrupted motion ; he therefore cautiously guards against critical remarks on it 

 in the following paragraph : 



" In this table, it was thought sufficient to use such exactness, as that 

 thereby (in drawing the lineaments of the nautical planisphere) sensible error 

 might be avoided. He that listeth to be more precise, may make the like table 

 to decades, or tens of seconds, out of Joachimus Rheticus his Canon Magnus 

 Triangulorum : notwithstanding the geometrician that desireth exact truth, 

 cannot be so satisfied neither ; for whose sake and further satisfaction, I thouht 

 good to adjoin also this geometrical conceit of dividing a meridian of the nauti- 

 cal planisphere. Let the equinoctial and a meridian be drawn upon a globe : 

 let the meridian, divided into degrees, minutes, seconds, &c. roll upon a 

 straight line, beginning at the equinoctial, the globe swelling in the mean 

 time in such sort, that the semi-diameter thereof may be always equal to the 

 secant of the angle, or arch contained between the equinoctial and semi- 

 diameter insisting at right angles upon the foresaid straight line : the degrees, 

 minutes, seconds. Sec. of the meridian, noted in the straight line, as they come 

 to touch the same, are the divisions of the meridian in the nautical planisphere : 

 and this conceit of dividing the meridian of the nautical planisphere may satisfy 

 the curious exactness of the geometrician ; but for mechanical use, the table 

 before mentioned may suffice." 



I have carefully endeavoured, says Mr. M., not to mistake the true sense and 

 meaning of Mr. West's proposition in any part of it ; if I have not, I cannot 

 pronounce what kind of chart may be formed from his tangent line being made 

 the line of latitudes, or that meridian line on which the tangents are to deter- 

 mine the sections of their respective parallels : I shall only observe, that if the 

 meridians be right lines, and parallel to each other, the rhumbs must be right 

 lines also ; but by this tangential projection, these will be deflected from their 

 true bearings, or make the angles of the courses too great, unless some expe- 

 dient be devised to accommodate this error ; and if the rhumbs be not right 

 lines, such chart will then be embarrassed with more difficulties in practice than 

 Mr. Wright's. 



XXI. Of a Species of Ophrys, supposed to he the Plant which is mentioned by 

 Gronovius in the Flora Virginica, p. 185, under the Name of Ophrys scapo 

 nudo foliis radicalibus ovato-oblongis, dimidii scapi longitudine.* By George 

 Dionysius Ehret, F. R. S. p. 8 1 . 



The root of this plant, from which many fleshy fibres branch, is composed of 



* Ophrys lilifolia. Lin, ? 



