Th: Jefferson presents his respects to the gentlemen of the committee on the Hessian fly, and prays their attendance at the Hall of the Philosophical society tomorrow (Friday) at half after seven P.M. He has conjectured that that hour will be most convenient to them, and that not a moment of their time may be lost unnecessarily, he will attend himself at the very moment precisely, and for their own convenience asks the same of them. He leaves town on Sunday for a month, to set out on a journey which will carry him through N. York and the whole of Long island, where this animal has raged much. He is therefore anxious to take with him the decision of the committee and particularly prays of Dr. Barton to have his queries prepared to present to them.