From the Philadelphia Ledger. The work at the Centennial grounds in Fairmount Park Í8 progressing vory rapidly. The northern portions of the permanent Memorial Hall, together with moet of the interior piers, is ready to receive the masoniy, while the southem front is now receiving attention. The front, facing the south, will be arranged with a central projection, as well as ono at each end, thus breaking the monotony of a continuous front of the long distance pre8Cribed for this porticn of the structure. Iu another portion of the park there has been completed a a large one story building, and litted up as a restaurant for tüe accoinmodation of themechanics who will soon be engaged in the eiection of the exhibition pavillion. Tool houses and carpenter shops dot the ground in every direction, and there are few spots in the city that present a scène of so inuch bustle and activity. For the exhibition building the levelling of the ground has nearly been completed. The storm of Saturday night inaterially assisted the surveyors and workmen in discovering the (hollows, as the water filled thein. Everything preparatory to the driving of piles for the pavillions will be completed by the coming week. In the meantime work has been commenced upon the wrought iron beams, the first of which are to be ready for delivery by the 15th of next ïnonth.