In the 1850's with the rapid decline of the whale hunting industry, whale oil for lamps became quite expensive... by the 1860's only the very wealthy could generally afford it if it even could be obtained. Thus many resorted to alternates such as using animal fats such as lard. Sometimes you will find round corded wick whale oil style lamps with very short burner tubes, The idea was to place the heat closer to the container so as to heat up the oil/lard so that it would flow more easily up the wick.
Frederick