Frorri the New Yoik WorM. The last rebel invasión of Marylar.J funnsheo anothor instanoe of tlio perils whiuh have come upon the country by tho m'gleot ol the part of the adiuiuistration of the warnings givon by General McClollan in the very first year of the war. Had the plans of that ofiiotT boon faithïully carried out, uut oi;u of the tour iiivasious of Marylaiid would have occurrod. Aí'ter he arrived on the peninua with bis army, and wliile he supposed General Banks was still under his ooinmai:ci, it will be remeuibered that he issuod au order to that offioer for Lia guidance in protecting Marylaiul and Wasbfiïgton froni any afctêmpt of the rebels by way of the Shenandöah valley. He had previously seflj Colouel Alexaoder witli direotions to see ïf fortifleationscould not bo throjvo Vip i" such of fhegapsof the Bluo mountaiYiSas would Sêïkiri a rebel aviny ir.arehing iuto Maryland from that dirootio. Gcueral liunks was directed to post his tvoops at certain poiuts. Ho v,-as a]so ordered to lioap his cavalry constantly in tnation down the valley of the Sher.ardoah, so as to bo wartied of any approach of the rebels. This order . was datcd Maroh 18, 18.2.; before, in fact, tho actual opening of the second eumpaign of the war. YVhen the administration relieved General McClellan of control over Gen eral Banks' army, they entirely overlooked the wiso pi'eeaulions which he took iu guarding the back-door of Washington. In fact, this Shenandoah vailey ia the true gate for an invasión of the Norlh, as the rebels subsequenïly diseoyered, and as General McCldlan's wise prescienee had foreseeu. When Mr. Linculn himself took the control of the ariuics out oif the hands of (iérieVal JIc (üeüai), ifl addition to ordering the latter officer to approach Eichtnond from the JS'orth, he aiso deached troopa fi om the Aniij of the Potomac, which were sorely -thosc under General McDoiell - to proteet, as he said, Washi. Hut where did he place these troops ? Iu tho Shenandoah valiey ? Nu ; they were louated at iredencKSburg, at wbich point thcy were of ab'out as much usti as tliey would havo been in Portland, Maine Tho forty thousand men under General McDowell were utterly throwo away, as was discovered when " Stonevvall " Jackson raade bis bis first fiimous raid lip the valley, driving back Bauks t: the Potomac river. The troips of General McDowell were utterly useless. " General'1 Lincoln had ingeniously managed to deplete our army by jut fuity thousand men. Tbey were enied to General McClellan, and put in positiou where tbey were of not the lightest use in defeading Washington. The curinus reader wbo will peruse Seneral McClellan's official report will tnow how clearly he foresaw, befo re the unpaigu opeued, that the Sbenandoab valley was the true line ofapproacli upou Washington. He will also remark how 'ar-seeing were the preparations he made o prevent the rebels ever certing beyond Jhester or Aldie gaps. If the reader vill fullow still further the course of tho oainpajgü in Virginia, be will find that vlmt General McClelian foresaw before he carnpaign opened, the adiuinistration las not been able to seo to this day. I'hey have not only failed to heed tho iositive warnings of General McCielian, )ut they have also failed to profit by the bitter expuiienees of the three years of var. Time and again bave tba rebel artnies snrged upon tbe Shenandoah valay, carryiiig dusolation to the homes of tbe people of Maryland and Pennsylva uia, and striking terror tbroughout the w.hole North because of tbo menace to the capital; yet to this day even the lightest precautions havo not been taken to guard against this disaster. Every time the rebels have advanced upon tbe valley ihey have not only not been iin jeded, but, through the most profound fatu[iidity, tbe admiuistration bas co'.lected stores of' all kinds at Martiiusburg "or thcir spocial acooniodation. We be lieve it cai be provcd that, in thoir varions raids up thu vulley the rebels liavo been able to pr.ieure stores to the arnount of ten nullions of dollars at that 0110 poiiit. The ïioi'thvTii ■ gafe of the valley bas never had ar.y sufficient forcé to guárd it, or a competent general to retará the progpess ut' tlio rebel ariuirs. ïuore is proiiiiiiiv tiot 'm all military bis toi'v so tnarked au' frtst'aiïCÖ of pveioiencé as tliut uhirh (iemral McCli-llan Sispkyai betere the eauipu'gn nppnci), m so consiicuouá ;in esa.uif.ile of dowunght stupidity as has beau shown by thu adininsratioQ in uot guardiqg thu f-iicnaTitloah valloy BJ as to prevent au invasión oí' the .Northeni Stilte. Thi.s (juality of fnrc-Mght aá to the conduet of the war iiiiukecl all of Gcneial McClullaii's military acts. It' the roader will petUVe his instrue'ions tq üiitlcr, h! will ti:i(1 that, iho w.R directod, iininediately upon tíio capturo of New Orleaus, to put h,- ;inny iu inolioi), aud tak e posse8ion of J;icks u, lbo capitu! of M ississippi, and furt ity it. If Butler. had oboyod tjeneral M cilülbm's orders, and had then taken Jaekson and lortified it, thü country can unders'.and what fi arl'al Iossls woult) have ben Maved iu the ivr! oa'tíiaigñ a'gainst Port H'id son aud Vicksburg.. In the vory fist yoiir di tbc war, tiio t !si ] regiqg v, oüld have been uU off i'roin tht' ■■■. ülrderat-y, and all the cat tlo auu of Te'xiiB would havo been iolt to tJie armies. Btfí BdfÏBr i'iï-rri d tq stay New Orleans, nnd quai rel uith wftnsVn and firuign consuls; and.to him Kt to bp weJitcd thü dreudful waste ol blood aud treasjire whieh tïie capturo ot' Vicksburíí ;ind Port Hadson fuLse'qüéotly entailed. In the orders to GcutüI Buell it wiil also be noticed that Gi MoQlelin poiiiteúout tp biui tbe in tanrá oí tli'ug, as soou t be oouíd, Easfern Te and fust thf ijantar of Knoxville and Nashville was of the first moment. ï!ie orders to General Shenuan touoliing what lie was cxpeeted to do at Port Royal reads liko a proph esy. What General McClellau said should be done was dono, simply because be foresaw tbat it was the ouly thing that oould bo dono. We cali attention to these facts because we realize how kuenly tbe country j has suffered siuce the soldiorstateir.an has beca withdrawn from tho military service of ' the country. Evory rebel vietory iu Marvlund and tho wasto of treasure aud life it costa to drive the enetny from that State, is au indictment fiiled with the most darnnir.g spaciücatioiis against the present military aiiniinistration at Washington.