A Mystery SolvedPittsburgh, May 13.—The numerous attempts during the past week to burn the “House of the Good Spepherd,” on Troy Hill, have created great interest, from the mystery surrounding the fires and the persistency of the iuceudiary. Saturday morning the sixth, and what will likely prove the last, incendiary fire there was kindled, and the incendiary c. ught almost in the act. As had been suspected for a day or two, the incendiary proved to be one of the trusted employes, a kind of upper servant, and candidate for admission to the sisterhood, a girl named Kate Clifford.The first fire occurred at 8 o’clock last Saturday morning a wees ; the second on Sunday a little past noon ; the third on Monday at 7:30 in the morning ; the fourth on Monday evening at 5:30 ; the fifth on Tuesday at 3:30 p. in., and the sixth on Friday at 10:30 in the forenoon. The investigations of Fire Marshal Stevenson re suited in ascertaining the following facts : Five minutes before the first fire two of the sisters had been iu the cellar where the fire was discovered, and there was none (here then ; when it broke out all the inmates were out of the building taking their regular re creation. When the Monday morning fire occurred all the inmates were in the chapel or at breakfast. Monday evening was the fire which caused the only damage, the loss being about $1,0(0. Then all the inmates were locked in their rooms, aud the sisters were in the chapel at mediation. It was evidently impossible that in this case the fire could have been started by one of the inmates of the Home ; that is, by any one of the persons who are kept there through charity. Tuesday the Fire Marshal was at the housebetween seven aud eight o’clock ia the morning, and examined all the sisters aud about au hour aud a half after this was over the fire broke out again. This was iu a place where it was utterly impossible for any of the inmates to get, a it was through the sisters’ private cellar. Alter this lire it became certain that some one who was | trusted was the guilty one, and on Wednesday morning the sisters were told to watch each other. This advice was taken by the sisters and faithfully carried out. Saturday morning two of the sisters went into the cellar about five o’clock and concealed themselves. Hetweeu nine aud ten o’clock they saw the girl Kate Clifford come into the cellar on an errand, attend to it. aud go out. About ten o’clock she came back into the cellar, opened a closet where were stored various inflammable articles, lighted a large piece of paper, threw it into the closet, aud shut the door. The two sisters immediately came out, aud were able to put out the lire before any damage was done, and without calling out the tire department.The incendiary, Kate Clifford, who was thus almo3t caught iu the act, was taken iu custody by the sisters, and the Fire Marshal and his Assistant were notified. They came to the house, aud after hearing all the particulars, ’Squire Eggers made an information charging Kate Clifford with arson, and the Fire Marshal committed her to jail to await trial. The girl is about eighteen years old, and came from Con-ueilsville to the house as a novitiate. The sisters had placed the mutt implicit trust iu her, aud she was the last one to he suspected. What motive sho had for the crime is iuconceivable. bhe says herself that she ouce §aw a man set lire to a house in Couneilfeville, and was the principal witness against him at hia trial. Since then she had been troubled with a coustaut desire or mania to commit the same crime.(