As tar as we kuow tliere are only a couple of fortresses in tlie province tliat. are at present in a defensivo condition. - On is the Cape Diamond Citadel of Quebec, with which every American traveler is familiar. It s without a doubt the strongest fortress in América - the strongest, possiblv, in the world, after thoae of Gibraltar and Cronstadt. The Citadel in built on the highest puint of Cape Diamond, at an elevalion of 350 ieet above the St. Lawrence, and on the river sido the clifiFs rise perpendicnlavly from the water. Ou all otlier sidus the city is so fortified by glacis, w.ille. trenchos, aud other works of defensc that a hostile approach is éeemed impossible by the best Britlsb authorities on military science. The city is also walled en tirely around, and is also protected by martello towers, of wliieh there are four eneirclii'g Quebec at cqual distance trom eaeh other. The Citadel of Quebec is ïlways kept in n condition of perfect re pair, but the outworks - that is the walls and worke about the city have been lowed of late to fall into ruin. In the event of war the defense of the city would not bo undertaken, as it would require fifteen or twenty thousaud men to man the walls. and the dofeiise of the Citadel would ;mswer all needful pur poses. For this, a garrisou of one thousand men, it is asserted, would be amply sufficient. There ia always storcd in the Citadel of Quebec sufficient piovisions to last its garrison for a siege oí seven yeari, It ilso coDtaius an inunMM qnautity oí war material, and to this quantity vury uuu8ual additions have been innde the present sumuier The old guns have bueu exchanged for rifled Armstrong eau non of the largest gize, and evwylbing tlnit prudeuce and foretbongbt could do has beei: doue to place the Citadol of Qucbeo in a tliorough Btate of uffiuietiey Al ii illustration of the trength of this place it may bo mentioned that in 1775, Monigomerv, the .Aineiiean General, suoceudid ii retobiag it whun the garrtwn was alraost dastitute of military f'oree, and the whole strength of tho Province only rmmbered 800 uien. The siege was a signal failure. In the first assault, as in those rentfwed during iabwouent vears, the Aiuericans were driven back aud t.Leir General killed, whila the lïrit ïsli are said to have lost only 006 oilkvr an 1 seventeen meu in killed and wounded. Another insurmoui.table obstacle to the invustineut of Quebeu is tha climate. For seven raoatha of tlio year it would be impossible for a hostilo anuy to Ciul provigions or to eucaiup in lbo vhnnity of Quebt'O. The theriüometer f;illa au low as 40 dogrees bclow zero, and the iubabitonts thcmselvei have to lay in their provisions bufore the inclemcut season sets in. The only otlier iortrcaes in Canada worthy of consideration are thoao on Navy Poiut and PointjUe.nry, wljioh oommand the harbor of Kingston. Fort Henry is tho principal work of dcfense. re uo also geveral inartello towers tícay it, aud as military post Kingston ia the strongest place iu Canada lifter Quebec. These forts it must bo rcmeinbered, havo always been kept in service able condition, aud if the reaulution to which the military authorities have come, uierely reíalos to their iuipcctiou, the act is simply one which is perfurmed with grcat regulanty at luast once a year. It is proper to add that on St. Helen's Island, opaosite Montreal, a n-giment of I soldiers is usually statianed Large quantities of ammuiiition are also atored there, and the Island miglit bs ued to great Eu'.vantage in tho defenbe of Moutreal the principal citylof the ('añadas.