DURTUBIE. See also the words _Platforms_ and _Battery_. _ROCKETS._—_Composition._ _Old Proportion._ | _New Proportion._ lbs. oz. | lbs. oz. Saltpetre 4 0 | — 4 4 Sulphur 1 0 | — 0 12 Charcoal 1 8 | — 2 0 ---------------------------------+---------------------- _Composition for the Stars._ | Mealed powder 0 lb. 8 oz.| Saltpetre 8 0 | Composition for rains Sulphur 2 0 | to head sky rockets Antimony 2 0 | is the same as the Isinglass dissolved 0 3½ | above for the Spirits of wine 1 pint. | rockets. Vinegar 1 quart. | ---------------------------------+---------------------- _General Table of Sky Rockets._ +---------------------------+--------+---------+--------+--------+ | |2 Pound.|1 Pound. |½ Pound.|¼ Pound.| +---------------------------+--------+---------+--------+--------+ | | Inch. | Inch. | Inch. | Inch. | | Exterior diameter | 2.13 | 1.69 | 1.34 | 1.06 | |Case Interior diameter | 1.529 | 1.214 | 0.961 | 0.761 | | Length before driving| 15.97 | 12.67 | 10.05 | 8.25 | +---------------------------+--------+---------+--------+--------+ |Length of guage | 1.5 | 1.25 | 1.0 | 0.75 | | for the choke | | | | | +---------------------------+--------+---------+--------+--------+ |Cylinders for Diameter | 2.84 | 2.25 | 1.79 | 1.39 | | heading Length | 4.26 | 3.38 | 2.68 | 2.12 | |Cones for Diameter | 2.84 | 2.25 | 1.79 | 1.39 | | heading Height | 4.26 | 3.38 | 2.68 | 2.18 | +---------------------------+--------+---------+--------+--------+ |Mallet for driving.—Weight | 4 lb. | 3 8 oz.| 2 1 | 1 10 | |Nᵒ. of Strokes | 31 | 21 | 18 | 13 | +---------------------------+--------+---------+--------+--------+ _Copper Ladles for filling Sky Rockets._ _Length_, 1½ the exterior diameter of the case. _Diameter_, equals the interior diameter of case. _Circumference_, ¾ the interior caliber of the case. Sky rockets are driven with composition up to 4½ exterior diameters of the case from the choke; and ⅕ of a diameter above the composition with good clay. They are bored and reamed up to 3½ diameters. _Dimensions of Sticks for Rockets._—General rules.