DIAGONAL TRUSSING. A particular method of binding and strengthening a vessel internally by a series of riders and truss-pieces placed diagonally. DIAMETER. In geometry, a right line passing through the centre of any circular figure from one point of its circumference to another. DIAMETER, APPARENT. The angle which the diameter of a heavenly body subtends at any time, varying inversely with its distance. The true is the real diameter, commonly expressed in miles. DIAMOND-CUT. _See_ RHOMBUS. DIAMOND-KNOT. An ornamental knot worked with the strands of a rope, sometimes used for bucket-strops, on the foot-ropes of jib-booms, man-ropes, &c. DIBBS. A galley term for ready money. Also, a small pool of water. DICE. _See_ DYCE. DICHOTOMIZED. A term applied to the moon, when her longitude differs 90° from that of the sun, in which position only half her disc is illuminated. DICKADEE. A northern name for the sand-piper. DICK-A-DILVER. A name for the periwinkle on our eastern coasts. DICKER-WORK. The timbering of tide-harbours in the Channel. Wattling between piles. DICKEY. An officer acting in commission.--_It's all dickey with him._ It's all up with him. DIDDLE, TO. To deceive. DIEGO. A very strong and heavy sword. DIE ON THE FIN, TO. An expression applied to whales, which when dying rise to the surface, after the final dive, with one side uppermost. DIET. The regulated food for patients in sick-bays and hospitals. DIFFERENCE. An important army term, meaning firstly the sum to be paid by officers when exchanging from the half to full pay; and, secondly, the price or difference in value of the several commissions. DIFFERENCE OF LATITUDE. The distance between any two places on the same meridian, or the difference between the parallels of latitude of any two places expressed in miles of the equator. DIFFERENCE OF LONGITUDE. The difference of any place from another eastward or westward, counted in degrees of the equator: that is, the difference between two places is an arc of the equator contained between their meridians, but measured in space on the parallel. Thus the difference of a degree of longitude in miles of the meridian would be-- At 20° lat. 56·4 miles " 40 " 38·6 " " 60 " 30·0 " " 80 " 10·4 " DIFFERENTIAL OBSERVATION. Taking the differences of right ascension and declination between a comet and a star, the position of which has been already determined. DIFFICULTY. A word unknown to true salts. DIGHT [from the Anglo-Saxon _diht_, arranging or disposing]. Now applied to dressing or preparing for muster; setting things in order. DIGIT. A twelfth part of the diameter; a term employed to denote the magnitude of an eclipse; as, so many _digits eclipsed_. DIKE. _See_ DYKE. DILL. An edible dark brown sea-weed, torn from the rocks at low-water. DILLOSK. The dried leaves of an edible sea-weed. (_See_ DULCE and PEPPER-DULSE.)