If the mortars, when loaded, are sent to any distance, or liable to be much moved, the firing powder should be secured from getting amongst the serpents, which would endanger the mortars, as well as hurt their performance. To prevent this, load the mortars thus: First put in the firing powder, and spread it equally about; then cut a round piece of blue touch-paper, equal to the exterior diameter of the mortar, and draw on it a circle equal to the interior diameter of the mortar, and notch it all round as far as that circle: then paste that part which is notched, and put it down the mortar close to the powder, and stick the pasted edge to the mortar: this will keep the powder always smooth at bottom, so that it may be moved or carried anywhere without receiving damage. The large single mortars are called _pots des aigrettes_. FIRE-PUMPS, OR ROMAN CANDLES. Cases for fire-pumps are made like those for tourbillons; only they are pasted instead of being rolled dry. Having rolled and dried your cases fill them: first put in a little meal-powder and then a star, on which ram, lightly, a ladle or two of composition, then a little meal-powder, and on that a star; then again composition, and so on till you have filled the case. Stars for fire-pumps should not be round, but must be made either square, or flat and circular with a hole through the middle: the quantity of powder for throwing the stars must increase as you come near the top of the case; for, if much powder be put at the bottom, it will burst the case. The stars must differ in size in this manner: let the star which you put in first be a little less than the bore of the case; but let the next star be a little larger, and the third star a little larger than the second, and so on: let them increase in diameter till within two of the top of the case, which two must fit in tight. As the loading of fire-pumps is somewhat difficult, it will be necessary to make two or three trials before you depend on their performance. When you fill a number of pumps, take care not to put in each an equal quantity of charge between the stars, so that when they are fired they may not throw up too many stars together. Cases for fire-pumps should be made very strong, and rolled on 4 or 8-ounce formers, 10 or 12 inches long each. CHARGE. lb. oz. lb. oz. Saltpetre 5 0 Saltpetre 5 0 Brimstone 1 0 Brimstone 2 0 Meal-powder 1-1/2 0 Meal-powder 1 8 Glass-dust 1 0 Glass-dust 1 8 AN ARTIFICIAL EARTHQUAKE. Mix the following ingredients to a paste, with water; bury it in the ground, and in a few hours the earth will break open in several places: lb. oz. Sulphur 4 0 Steel-dust 4 0 _Chinese Fountains._