A lady correspondent writes to us, giving her idea of tbe philosophy of the facts recorded in our recent article on this snbject. We will give a condensation of her letter, which is to the effect "that heat is never strictly speaking evolved by the agitation of water; bnt, the cause of elevation of temperature, when water flows along shutes, tubes, or is shaken in a patent churn, is due to the friction of the globules of water against the solid material with which they are in contact." She finds fault with us for saying anything against poetical expressions, and, as a lady only can, defends the poets from the charge of writing false science, in such a manncr that we must refrain from argument, hoping, however, to hear from her again.