Among all the works published by the firm perhaps the most useful was, and indeed is, the _Popular Educator_; in this, for the weekly sum of one penny, the vast store-house of human knowledge was thrown open; the matter, carefully systematised and arranged so as to encourage self-tuition, aided many a struggler in the path of progress. This was ably followed by the _Technical Educator_. In the former of these works Lord Brougham took an immense interest, and his opinion of John Cassell was as pleasing as it was often repeated. Of the illustrated works issued in the same cheap method many were English, or rather European, classics, such as the “Pilgrim’s Progress,” “Don Quixote,” “Foxe’s Book of Martyrs,” “Shakespeare,” “Robinson Crusoe,” “Gulliver’s Travels,” &c. Like Tegg or Lackington, Cassell must be looked upon rather as an encourager of the reading than of the writing world; but among the works claiming originality as well as cheapness, the _History of England_ is perhaps the best; the _Natural History_ is well printed, well illustrated, and, as far as regards the more legitimate department of the publisher’s trade, worthy of praise; the “letter-press,” or literary portion, has, however, been much criticised. The _Family Paper_ and the _Quiver_ attained a very wide circulation, and while the latter is still one of the most favourite distinctly religious serials of the day, the former, until it was changed into the _Magazine_, held faithfully to its promise of pure and wholesome literature. In furtherance of his various schemes, Cassell often travelled, particularly to France, where he was well known, and where he was thus enabled to effect a very considerable business in the exchange and purchase of illustrations for his various works. In 1859 he visited America, and, with the reputation that preceded him, met with a very flattering reception. On his return, with the energy that distinguished his character he started a company for the manufacture of petroleum, which was the first in England to recognise the value of the new discovery. He also published a series of articles entitled “America as it is,” in which the contest between North and South was discussed with a keenness of vision that results proved to be correct and almost prophetic.