Stories of Great Scientists - Charles Gibson

The Reverend Dr. Joseph Priestley

The Clergyman-Philosopher

Those of us who made a hobby of Chemistry in our boyhood will associate the name of Priestley with the discovery of Oxygen. One of the early experiments of the amateur chemist is to heat some potassium chlorate and manganese dioxide in a glass flask and draw off a plentiful supply of oxygen gas. If the young chemist is a thoughtful lad, and is not content merely to watch all sorts of things burning in oxygen with an intense brightness, he will soon become impressed with the tremendous importance of oxygen in Nature; it is the most abundant of all the elements. I remember being very much interested to learn that it was a clergyman who discovered oxygen, and the name of the Rev. Dr. Joseph Priestley was permanently fixed in my mind. But this discovery is by no means the only claim which Priestley has for a place among the Heroes of Science.

In the preceding chapter we found that because Benjamin Franklin was a very active politician, it was necessary for our present purpose to pass over a very large part of his life. We have to deal with Priestley in the same fashion, as he was a very active clergyman, and his voluminous works on Theology do not come within our present interest.

We are fortunate in having something akin to an autobiography left by Priestley, just as we had of Franklin. The opening sentence of Priestley's Memoirs is of interest: "Having thought it right to leave behind me some account of my friends and benefactors, it is in a manner necessary that I also give some account of myself; and as the like has been done by many persons, and for reasons which posterity has approved, I make no further apology for following their example." So said the Rev. Dr. Joseph Priestley, and how very different is his attitude from that of a French Scientist who published a book under the title Lives of Distinguished Scientific Men, and whose first chapter is "The History of my Youth."

Priestley's father was a maker and dresser of woollen cloth, and his mother was the daughter of a farmer. His parents were well-to-do, but not wealthy. Joseph was only six years of age when his mother died, but he could remember the very strict manner in which she trained him. On one occasion she happened to find him playing with a pin, and on learning that he had brought the pin from his uncle's house, she sent him back with it, not because of the value of the pin, although they were all hand-made in those days, but, as Priestley remarks, in order to impress upon his mind "a clear idea of the distinction of property."

Joseph Priestley was born near Leeds in 1733, six years after the death of Sir Isaac Newton. As we shall find Priestley meeting Benjamin Franklin later, it is of interest to note that when Priestley was born, Franklin would be about twenty-seven years of age.

At the death of Mrs. Priestley her husband was left with the care of six little ones, so he allowed an aunt who had no family of her own to adopt Joseph, he being then six years of age. Our hero speaks very highly of this aunt, who sent him to the best local schools, where he mastered Latin and Greek very quickly. By the time he had reached his sixteenth year he was an excellent classical scholar, and during the holidays he learnt Hebrew. Priestley did not merely master classics in the sense in which we learn these languages at school or college; he was able to correspond in Latin, and he was so far advanced with his self-taught Hebrew that he was able to act as teacher of it to a clergyman, who in return taught Priestley Chaldee, Syriac, and Arabic. But at the age of sixteen his health became unsatisfactory and he had to abandon his academic career.

It was thought that a business life would be best for his health, so he set himself to learn modern languages that would be useful for such a purpose. Without any assistance he acquired a thorough knowledge of French, Italian, and Dutch. Very soon he was able to write and translate business letters in these languages for his uncle. This must have been very pleasing to the uncle, but his aunt had set her heart upon Joseph being a clergyman. By the time he was twenty years of age his health had improved so much that his aunt sent him to an academy, where he could continue his former studies with a view to becoming a clergyman.

electrical machines


Priestley tells us that as a boy he was of a very serious turn of mind. Of course, his aunt was very strict about all religious matters, and in common with the people of that time she kept the Sabbath very strictly. Priestley tells us "no victuals were dressed on that day in any family, no member of it was permitted to walk out for recreation, but the whole of the day was spent at the public meeting, or at home in reading, meditating or prayer." But his aunt, who was a Nonconformist, was not narrow-minded; Priestley tells us "her house was the resort of all the Dissenting ministers in the neighbourhood without distinction," and that even those who were most obnoxious to the people because of their heresy were made welcome so long as the worthy lady believed them to be honest and good men. Priestley was allowed to hear the conversation of these visitors, and possibly it was this freedom of thought which made him question religious ideas on his own account.

Priestley was soon equipped for the duties of a clergyman, but he could not conform his opinions to all the ideas then accepted by the Church, and so, when he got a call to a small country church, he did not become popular. Another drawback to popularity was an impediment in his speech, which hindered him greatly as a preacher. The young clergyman was greatly distressed by this physical defect, and he did all in his power to overcome it; indeed, he persuaded his aunt to spend twenty guineas in sending him to London to be cured by a quack who advertised certain cure, but unfortunately, when he returned, he found that his speaking was worse than ever.

In this small country charge he had a nominal salary of forty pounds, which in point of fact never exceeded thirty pounds, and on occasions fell far short of that. For a time he was dependent upon charitably disposed friends sending him an occasional five-pound note to help him out. Priestley's aunt knew of the smallness of clergymen's salaries, and she had promised that if Joseph would become a minister she would leave him quite independent of his salary. But it came about that a niece who was deformed required the money, and Priestley was quite agreeable that the promise should be cancelled, and the money given to this girl who could not be expected to make her own way in the world. He says that his aunt had given him a good education, which was even more valuable than giving him an estate.

After three years in his first charge the Rev. Joseph Priestley, then twenty-five years of age, received a call to another country district. This removal meant a journey from Suffolk to Cheshire, and travelling in those days was quite an undertaking. A man going from London to Manchester might take so long as a fortnight, for there was no stage-coach, and the traveller had to depend upon some travelling merchant who transacted business in the different villages as he went along. Even at the time when Priestley's Memoirs were published, after his death, it took the stage-coach a day and a hall to go over the wretched roads from London to Manchester; a journey we can make nowadays in less than four hours.

When Priestley was settled down in his second charge he augmented his salary by teaching. He had a school of thirty boys and half a dozen girls. He was busy teaching from 7 a.m. to 4 p.m., with only one hour for dinner, and at 4 p.m. he went straight from school to private tutoring, from which he was not free till 7 p.m. In addition to these twelve hours of activity, he studied, and even began his literary work. Of course, he would have the sermons which he preached in his previous charge, but it should be noted that through all his busy life he never neglected his duties as a clergyman; he tells us that he always counted these duties his greatest honour.

But what set this clergyman on the track of Science? Of course, one might say of Joseph Priestley, as of Benjamin Franklin, that he was a born philosopher, but up till the time of Priestley's second charge he does not seem to have paid any particular attention to Science. In order to add to the popularity of his school he bought some scientific apparatus, by means of which he taught his pupils something of natural philosophy. He tells us that he taught the scholars in the senior class to take charge of the apparatus, and he allowed them to entertain their parents and friends with experiments. In this way he considerably extended the reputation of his school.

After three years in his second charge, Priestley was appointed classical teacher in the Nonconformist Academy at Warrington. Here he passed six of his happiest years, having more leisure to give to his literary work. At the age of thirty he married the daughter of an ironmaster, and his married life was a very happy one, as is witnessed by one of his sons, who edited his Memoirs.

While at Warrington Priestley visited London, where he met the famous Benjamin Franklin, with whom he became very intimate. Franklin encouraged Priestley to write The History of Electricity, which in one's bookshelves to-day looks exactly like an old family Bible. I remember, on going through a lot of old books in a library many years ago, being very much surprised to find this History and Present State of Electricity, with Original Experiments. It was the date, 1767, that surprised me, for it meant that this big, bulky book had been written a generation before the discovery of the electric current, when man knew only of electrified bodies. This great book was written in less than one year, during which time Priestley had to lecture on classics for five hours each day. While writing it he kept sending on the manuscript to his friend Benjamin Franklin to read. About this time Priestley received the honorary degree of LL.D. from Edinburgh University, and a little later he was elected a Fellow of the Royal Society of London, because of his researches in Electricity.

After six years' residence in Warrington Priestley accepted a call to Leeds, where he devoted much time to theological writings, and in addition to overtaking all his ministerial duties, he was able to devote some time to chemical researches. I was about to say—to a study of Chemistry—but this Science scarcely existed at that time. One is apt to forget how recent is the Science of Chemistry. A few years ago a very learned Chemist remarked to me that many years ago, when he was a young man, he could boast that he knew the whole of Chemistry. Now the Science has advanced so far that, with all his great increase of knowledge, he could by no means repeat the same boast to-day.

Priestley's name is very definitely associated with the subject of "different kinds of air," which was the way in which the different gases were described in his day. It is interesting to note how this subject, which helped to make him famous, was first brought before his notice. He tells us that it happened through his living in a house next a brewery, and that he began by amusing himself with experiments on the "fixed air" produced in the brewery. This "fixed air" is no other than our well-known carbonic acid gas, which serves many useful purposes, although it will not support life or combustion. Priestley received a gold medal from the Royal Society for his research work on gases.

While acting as clergyman at Leeds, it was proposed that Priestley should accompany the famous Captain Cook on his second voyage to the South Seas, but objections were raised because some of Priestley's religious ideas were considered to be unorthodox. How this should be a disqualification for such a scientific post it is difficult to imagine.

Remembering what an important part the Grand Dukes of Tuscany played in the life of Galileo Galilei, it is of interest to note that Joseph Priestley, living one hundred years after Galileo, received a request from the then Duke of Tuscany to have made for him in England a very large electrical machine.

We may be surprised to find our scientific clergyman leaving his college lectureship to go into the household of the Earl of Shelburne, afterwards Lord Lansdowne, who was a Cabinet Minister in the reign of King George III. Priestley tells us that he was nominally Librarian to Lord Shelburne, but that in point of fact he was merely a companionable friend. Needless to say that Priestley had no desire for a life of ease or luxury. What concerned him was that he could get on with his important theological works, which he could not otherwise write, nor publish at his own expense. This must have been a considerable sacrifice to Priestley, for it meant separation from his family during the whole of the winter months.

After having been with Lord Shelburne for six years, Priestley accepted a call to a Dissenting church in Birmingham. He was at this time about forty-seven years of age. It seemed as though all would go well in the new circumstances. He had many friends, and he became a very active member of a small Scientific Society named The Lunar Society. This Society was kept very select, there never having been more than eight or ten members at any one time. They met at each other's houses for dinner once every month. The day of the meeting was the Monday nearest the full moon, and Priestley gives as the reason for this, "in order to have the benefit of its light in returning home." It was this arrangement that gave the name to the Society, and not any idea of making a special study of lunar matters. Of course, the moonlight was of considerable importance to pedestrians in those days, for William Murdoch, the manager of James Watt's engine works, and a member of this Society, had not invented the use of coal gas as an illuminant at that time.

These dinner-parties were begun at two o'clock in the afternoon, and the meetings did not break up till eight in the evening. There was nothing of a religious or political connection; the subjects of discussion were confined to Literature, Science, and Art. Priestley says the members were "united by a common love of Science, which we thought sufficient to bring together persons of all distinctions, Christians, Jews, Mahomedans, and Heathen, Monarchists and Republicans." In the list of members we find the names of James Watt, his partner, Matthew Boulton, and, as already stated, their works manager, William Murdoch. Another member was Dr. Erasmus Darwin, grandfather of the famous Charles Darwin, whose life we shall consider later. Other members whose names are familiar to us were William Herschel, the Astronomer; Josiah Wedgwood, the Potter; and Thomas Day, a wealthy and eccentric philanthropist, best known to us as the author of Sandford and Merton. This gentleman was killed in 1789 by being thrown from his horse while riding.

In connection with this Lunar Society there is an interesting letter from James Watt to Charles Darwin's grandfather:

"I beg that you would impress upon your memory the idea that you promised to dine with sundry men of learning at my house on Monday next, and that you will realise the idea. For your encouragement there is a new book to cut up, and it is to be determined whether or not heat is a compound of Phlogiston and empyreal air, and whether a mirror can reflect the heat of the fire. I give you a friendly warning that you may be found wanting whichever opinion you adopt in the latter question; therefore be cautious. If you are meek and humble, perhaps, you may be told what light is made of, and also how to make it."

It is particularly interesting to note the primitive ideas held by our great-grandfathers concerning the nature of Heat and Light. We shall see later how Humphry Davy, when a lad, demonstrated that Heat was not a material thing.

Priestley's remark, already quoted, that the Society was open to Monarchists and Republicans has special significance. These were the days of the French Revolution, and Priestley was, of course, on the side of the Revolutionists. It so happened that some of those of similar sympathies in Birmingham held a dinner on the anniversary of the taking of the Bastille, but Priestley tells us that he had nothing whatever to do with this celebration. Nevertheless, an unreasoning mob attacked his chapel and his house. They had no respect for the reverend gentleman's valuable manuscripts. These they tore to pieces, and arranged to make a bonfire of them and the house. Some of the crowd made a vain attempt to light the mass with sparks from one of Priestley's large electrical machines. Fortunately, before the house was attacked its occupants were at a safe distance, but it must have been a shock to Priestley to see his house, his papers, and his apparatus utterly destroyed by fire.

Priestley gives us an interesting account in his Memoirs of those times. His friends advised him to fly to France for protection, but the most he would permit was the taking of a place for him in the London coach in another name. However, the friend who had the courage to receive him in London had thought it necessary to provide a dress that should disguise him, and also a method of escape should the house be attacked, and for some time he would not permit him to go out of doors.

When Priestley decided to settle in London, he found it almost impossible to get a house, which in the end had to be taken in the name of a friend. The landlord declared that he was running a great risk, for not only did he believe that this house would be destroyed, if it became known that Priestley was there, but in addition he thought the crowd would proceed to the landlord's own residence, although it was twenty miles out of London.

For three years Priestley acted as clergyman in a small chapel at Hackney. Of course, he had a perfectly clear conscience, and it is doubtful if ever he would have left London on his own account, but he found that his sons were being persecuted also, merely because they were his sons. Chiefly for that reason he determined to emigrate to America.

The strong feeling against Priestley was not all contained within the unreasoning mob at Birmingham. He tells us that at a dinner of all the Prebendaries of a cathedral-church the conversation happened to turn on the riots in Birmingham, and that a clergyman stated that if Priestley were mounted on a pile of his own publications, he (the clergyman) would willingly set fire to them and burn the author with them, whereupon all the party present declared that they would be willing to do likewise. By this time Priestley was shunned by the Royal Society, but entirely on account of his religious beliefs.

Even more important than Priestley's chemical researches was the tremendous impetus which he gave to the Science of Chemistry, which was then only in its infancy. We should remember that Priestley had to invent his own chemical apparatus.

In 1794, at the age of sixty, the Rev. Dr. Joseph Priestley sailed for New York, the voyage taking about two months, which seems to have been a good average passage in those days. His reception in the young States was very cordial. He received addresses from the Scientific Societies. He was offered the post of Professor of Chemistry in the University of Pennsylvania, and, although he declined it, he was offered the Principalship at a later date, which he felt he must decline also. He settled down in Philadelphia, the home of Benjamin Franklin, who had died a few years earlier.

As evidence of the great intimacy which had existed between Franklin and Priestley, it may be mentioned that the day before Benjamin Franklin left Great Britain for the last time he spent with Priestley alone.

There is one statement in Priestley's Memoirs regarding Franklin which I can never understand. It reads: "It is much to be lamented that a man of Franklin's general good character, and great influence, should have been an unbeliever in Christianity, and also have done so much as he did to make others unbelievers." This statement is surprising, and seems to be contradicted entirely by Franklin's own statement (see page 162); indeed, it seems to me that what one might pick out as being unorthodox in Franklin's religion is to be found also in that of Priestley's. There has surely been some misunderstanding!

Priestley was a very active man up to the last days of his life, although he was practically an invalid for the last two years. His mind, however, remained perfectly clear, and in this connection it is surprising to find that in his prime he had been subject to very strange lapses of memory. He would write upon a subject, and then find later that he had already published the very same ideas, and had performed experiments which he was now giving as new. He tells us that on one occasion he had written and published an article in pamphlet form, and was almost terror-stricken to come across the manuscript of an identical article in his desk, as to the writing of which he had not the faintest recollection. Even on referring to his own published writings he sometimes came across passages which seemed to be entirely new to him.

All through life Priestley took entire charge of his own laboratory, not even allowing a maid to kindle his fire. The old gentleman usually had this done before the other members of the household were astir, and throughout life his most serious work was always done in the mornings.

He lived to see Volta's discovery of the electric current, and in his closing years he made experiments with Volta's Pile, the original of all electric batteries. He was busy writing on theological subjects up to the very end of his life.

The description of Priestley's last days, as given in the Memoirs by his son, makes interesting reading. The old gentleman was perfectly aware that he was dying, and he very quietly tried to arrange his unfinished work to make its completion as easy as possible. He stopped the printing of a second volume that the third might be commenced, as otherwise he would not see that it was started on the lines that he wished. He called his grandchildren to his bedside before they went off to bed, and he told them that he, too, was going to have a sleep, a very long sleep, but that he would meet them again in another world. He made all arrangements, just as though he were merely going off on a long journey, and so he slept away at the age of seventy years, in the presence of his son and his son's wife, his own wife having predeceased him about ten years earlier.