Some websites have the passenger lists from J & J Cook, Shipping Agents, online. I haven't seen it posted yet for the year 1864. Your library may be able to get the microfilm or book.
J.& J. Cooke fonds Library and Archives Canada Fonds consists of three volumes of passenger lists of Irish emigrants for the period: 1847-1849, 1850-1857, and 1858-1867. Passengers were bound for St. John, New Brunswick, Quebec or Philadelphia. 2 microfilm reels
Irish passenger lists, 1847-1871 : lists of passengers sailing from Londonderry to America on ships of the J. & J. Cooke Line and the McCorkell Line Author: Brian Mitchell Publisher: Baltimore : Genealogical Pub. Co, 1988. 333 pp.