Taken from pieces written for a periodical which he both founded and produced, it is normally published in two volumes: the first covering those articles published in the years 1873 and 1876, the second covering those published in the years 1877, 1880 and 1881.
This compilation originates from articles he both authored and produced for a periodical. It is typically published in two volumes: the first volume includes pieces from 1873 and 1876, while the second covers those from 1877, 1880, and 1881.