They consist, as will be seen, of five descriptions, but the 10-inch is considered, on the score of economy, as equal to all useful purposes. The French have, at various times, constructed mortars of enormously large dimensions, but certainly with no useful result. The monster mortar, used at the siege of Antwerp, fired only ten or twelve shots, and with comparatively little effect. It burst some time after, while under a course of experiment, with a considerably less charge than it had formerly withstood; thus affording one very conclusive and illustrative fact in the theory of vibrations in metals: for there can be no question but that the shell, from the smallness of the charge, was too long detained in the mortar; the waves of vibration caused by the explosive force moving so rapidly through the mass that the metal at last lost its cohesive nature from their very rapid succession. It will be perceived, on reference to the adjoining tables, that ranges are obtained by the modifications of charges. ENGLISH MORTAR PRACTICE.[3] [3] Artillerist’s Manual. --------------------------------++--------------------------------+ 13-INCH IRON. || 10-INCH IRON. | Weight, 16 cwts. || 16 cwts. 2 qrs. | Shell filled, 200 lbs.[4] || 92 lbs. | Bursting powder, 6 lbs. 2 ozs. || 2 lbs. 10 ozs. | Blowing powder, 2 ozs. || 1-1/2 ozs. | -------+-----------+-----+------++-------+-----------+-----+------+ Ele- | Charge. |Fuse.|Range.|| Ele- | Charge. |Fuse.|Range.| vation.| | | ||vation.| | | | -------+-----------+-----+------+--------+-----------+-----+------+ deg. |lbs. ozs. |inch.|yards.|| deg. |lbs. ozs. |inch.|yards.| 45 | 2 1-1/2| 1·90| 450|| 45 | 1 0-1/2| 1·90| 450| | 2 3 | 2·00| 500|| | 1 2 | 2·00| 500| | 2 4-3/4| 2·10| 550|| | 1 3-1/4| 2·10| 550| | 2 6 | 2·20| 600|| | 1 4-3/4| 2·20| 600| | 2 7-3/4| 2·30| 650|| | 1 6 | 2·30| 650| | 2 9-1/2| 2·40| 700|| | 1 7-1/2| 2·40| 700| | 2 11-3/4| 2·45| 750|| | 1 9 | 2·45| 750| | 2 14 | 2·50| 800|| | 1 10 | 2·50| 800| | 3 0-1/2| 2·55| 850|| | 1 11 | 2·55| 850| | 3 3 | 2·60| 900|| | 1 12 | 2·60| 900| | 3 5-1/2| 2·65| 950|| | 1 13 | 2·65| 950| | 3 8 | 2·70| 1,000|| | 1 14 | 2·70| 1,000| | 3 10 | 2·75| 1,050|| | 1 15-1/4| 2·75| 1,050| | 3 12 | 2·80| 1,100|| | 2 0-1/2| 2·80| 1,100| | 3 14 | 2·85| 1,150|| | 2 1-3/4| 2·85| 1,150| | 4 0 | 2·90| 1,200|| | 2 3 | 2·90| 1,200|