. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . s, the diagonal P P of which isvertical to the plane of the mirror ; this rhombus is constructed in such a manner that one of itssides is parallel to D O, that is to say, parallel to the rays of incident, whence the reflecting raysbecome parallel to the other side of the rhombus. By means of a second limbus R R, which can befixed in its position by the screw V, the inclination of these reflecting rays can be changed ; andin order to bring these rays into al
. Spons' dictionary of engineering, civil, mechanical, military, and naval; with technical terms in French, German, Italian, and Spanish . s, the diagonal P P of which isvertical to the plane of the mirror ; this rhombus is constructed in such a manner that one of itssides is parallel to D O, that is to say, parallel to the rays of incident, whence the reflecting raysbecome parallel to the other side of the rhombus. By means of a second limbus R R, which can befixed in its position by the screw V, the inclination of these reflecting rays can be changed ; andin order to bring these rays into all possible azimuths, the limbus R R is carried upon a hollowshaft A, wlüch contains, besides the transferring mechanism of the time-piece, the moving 1880 HINGING. mechanism for the needles and the other limbus DD; this shaft A can be fixed by the hand-screw V. A pinule e and a screen P are arranged in such a manner that the chord e P is parallelto O D, whence the ray that passes through e arrives always at P as soon as the apparatus isregulated. This circumstance or condition may be used, on the other hand, for placing the axis in. the meridian by means of setting the time-piece correctly, making the arc B D equal to the comple-ment of the declination, and by turning then the apparatus upon its base-plate until the ray of thesun is seen to pass from e to P. A similar arrangement is adopted in M, Foucaults heliostat, andmay be fixed to all other ones. Fig. 3951 is of a heliostat made by Elliott Bros., London. HELIX.^ Fe., Hélice ; Ger., Schraubenlinie, Spirale ; Ital., Elice ; Span., Hélice. A helix is a curved line of double curvature, a spiral line, as of wire in a coil. A knowledgeof twisted surfaces, that have helices to guide the generating straight line, is indispensable in designing screw-propellers. The equations of the helix are x a COS. -- and yh za sm. 7 •h X, y, 2r, being the co-ordinates of any point in the twisted surface. See Aechimedian HI
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Keywords: ., bookcentury1800, bookdecade1870, bookidsp, booksubjectengineering
