Page 35, para. 3, line 1, for “_sulphurate of Potassia_” read “_sulphide of Potassa_.” Page 36, para. 4, lines 1 and 2, for “_which is a mortar_” read “_the chamber being_.” Page 40, last line but 3, for “_Polyreetes_” read “_Polyorcetes_.” Page 41, para. 4, line 10, for “ix” read “xii.” Page 53, para. 2, line 9, for “_incredible_” read “_incredibly_.” Page 66, para. 6, line 2, after “_has_” insert “_a_” Page 78, para. 5, line 3, for “753in.,” read “·753in.” Page 78, para. 5, line 3, for “16” read “14¹⁄₂.” Page 79, line 4, for “600” read “6,000.” Page 84, para. 2, line 1, for “_Latinat_” read “_Catinat_.” Page 84, para. 3, line 1, for “_masquitairy_” read “_mousquetaires_.” Page 86, para. 10, line 2, for “_Carabins ragees_,” read “_Carabines rayées_.” Page 86, para. 12, line 1, for “_subaltern officers_” read “_Non-Commissioned Officers_.” Page 89, line 3, for “_range_” read “_rayé_.” Page 89, line 3, for “_ball culot_” read “_balle à culot_.” Page 91, para. 4, last line, for “⁷⁄₁₀₀” read “¹⁄₁₀₀” Page 93, para. 8, line 1, for “_wounds_” read “_rounds_.” Page 98, para. 1, lines 6 and 7, for “_possible. For_,” read “_possible; for_” Page 103, para. 3, line 7, for “_proportionary_” read “_proportionate_.” Page 103, para. 5, line 4, for “_reserved_” read “_reversed_.” Page 105, para. 6, line 3, for “_horn-wood_” read “_hora, wood_.” Page 112, para. 1, line 8, after “_direction_,” insert “_b_.” Page 114, para. 2, line 7, for “16-48-80” read “16+48+80.” Page 115, para. 2, line 2, for “_sine_” read “_tangent_.” Page 115, para. 2, for “_plate_ 21, _fig._ 3,” read “_plate_ 22, _fig._ 3.” Page 119, para. 3, line 1, after “_moving_,” insert “_in_.” Plate 21, fig. 5, should be lettered as fig. 4. plate 22. HISTORY OF GUNPOWDER. The History of Gunpowder may well form a prelude to that of Fire Arms, as the existence of the latter is wholly dependent on the discovery of the former. Of all the discoveries which have been made, there is, perhaps, none which has produced more important consequences to mankind than the discovery of Gunpowder, as by introducing fire-arms, and a new method of fortifying, attacking, and defending Towns, it wrought a complete change in the whole art of war. ~Knock’s opinion.~ The invention of Gunpowder is completely involved in obscurity, and this very fact is one great proof of its antiquity. Knock observes that the invention of Gunpowder comprises several discoveries, which it is necessary to distinguish from each other. ~Order of discovery.~ 1st.--The discovery of Nitre, the principal ingredient, and the cause of its detonation. 2nd.--The mixture of nitre with sulphur and charcoal, which, properly speaking, form gunpowder. 3rd.--The application of powder to fire-works. 4th.--Its employment as a propelling agent for throwing stones, bullets, &c. 5th.--Its employment in springing mines and destroying fortifications.