The piece on Perspective was published in 1770, under the title of “A Familiar Introduction to the Theory and Practice of Perspective. With copperplates.” He gave as his reason for writing it that, having occasion to make drawings of philosophical instruments and apparatus he had felt the need of a work treating of perspective. It will be seen in the various editions of his works that the words “Priestley del” are engraved at the left-hand corner of the copperplates of the illustrations. The book had a considerable sale and was frequently recommended by drawing-masters. A second edition appeared in 1782 and it continued to be used well into the nineteenth century.

It is interesting to note that the first printed account of the use of india-rubber for the purpose of erasing lead pencil marks occurs in the preface to this work. It ran thus:—

“Since this work was printed off I have seen a substance excellently adapted to the purpose of wiping off from paper the marks of black lead pencil. It must therefore be of singular use to those who practise drawing. It is sold by Mr Nairne, mathematical instrument maker, opposite the Royal Exchange. He sells a cubical piece of about half an inch for three shillings, and he says it will last several years.”

The “bolder push than ever for the pillory, the King’s Bench Prison, or something worse,” probably refers to the anonymous pieces which he published in support of “Wilkes and Liberty” in the course of the memorable struggle between the freeholders of Middlesex and the House of Commons concerning the rights of free representation by parliamentary constituencies which at that time agitated the country. Wilkes had shortly before the date of this letter been fined by the King’s Bench £1000 and sentenced to twenty-two months’ imprisonment for publishing an impious libel, and had been expelled from the House of Commons—to which, however, he was repeatedly returned by the electors of Middlesex.

The Richmond visit to Archdeacon Blackburne, whose son had been at the Warrington Academy, is memorable from the circumstance that on its occasion Priestley first met Theophilus Lindsey, with whom he contracted an intimate and lasting friendship, which greatly influenced the lives and fortunes of both, and of which Priestley subsequently wrote that it had been a source of more real satisfaction to him than any other circumstance in his whole life.

The busy pamphleteer found time, however, to put together more ambitious works than Wilkes and Liberty. The success of his History of Electricity induced him to attempt the compilation of the history of all the branches of experimental philosophy, and he made proposals to publish a History of Discoveries Relating to Vision Light and Colours. The subscription to this work was not, however, sufficient to induce him to proceed, and after a considerable outlay in the purchase of books and other material the project was abandoned.

Priestley was, perhaps, the most industrious bookmaker of his age. Boswell indeed dubbed him a “literary Jack-of-all-Trades,” and he was busy with proof-sheets even to the day of his death. In fact, the closing act of his life, before he put his hand to his face to hide the last flicker of the vital spark, was to make a correction in a proof-sheet. He usually composed in shorthand, and much of this work was done in the family circle, sitting by the parlour fire. Conversation never disturbed him. Although his style is somewhat prolix, his language is simple and direct and his meaning invariably clear. Charges that his writings were hasty performances in nowise disturbed him. Indeed, he was wont to say that some of those that were most hurriedly done were among those that were best received. Whatever might have been the time he spent on their composition he was confident that more would not have contributed to their perfection in any essential particular, and about anything farther he was never very solicitous. His object, he said, was not to acquire the character of a fine writer but of a useful one. Pecuniary gain was never the chief object of his work; several of his books, indeed, were written with the prospect of certain loss. Many writers before and since the great lexicographer have left us what they have imagined to have been the secret of their success as literary craftsmen, and have told us of the means by which they gained their proficiency of composition and mastery of style. Priestley has no pretensions to be considered a master of style; nevertheless, it is of interest to learn how he acquired facility in writing the simple, unaffected English which characterises his literary work. It came, he said, from a practice of committing to writing as much as he could of the sermons he heard, and of composing much in verse. With regard to the sermons, he says:—

“This practice I began very early, and continued it until I was able from the heads of a discourse to supply the rest myself. For, not troubling myself to commit to memory much of the amplification, and writing at home almost as much as I had heard, I insensibly acquired a habit of composing with great readiness, and from this practice I believe I have derived great advantage through life, composition seldom employing so much time as would be necessary to write in long hand anything I have published.”

As regards the verses, he says:—

“I was myself far from having any pretension to the character of a poet, but in the early part of my life I was a great versifier, and this, I believe, as well as my custom of writing after preachers, mentioned before, contributed to the ease with which I always wrote prose.”