FROST I NT JULY.Our friends from the country inform us,- that on Monday morning* frost was visible in low lands. The cool weather of the four or five last days has given a check to vegetation. Our accounts from Maine, Vevfr Hampshire and. Vermont, on this subject are melancholy. Showers and heat may yet revive the husbandman- but a wiie forethought will take measures to guard against a scarcity of bread com.—Boston Centinel, 10th inst.