“The work having been written at various times, and in various places, tautology has crept into many parts of it; and I fear some are more condensed than they should be in a system of familiar philosophy. Originality, or the pride of discovery, has not led me beyond the bounds of what I believe to be truth. The identity of fire, light, heat, caloric, phlogiston, and electricity, or rather their being but modifications of one and the same principle as well as their being the grand agents in the order of nature; these are the leading problems of the work; and the parts which have, in a great measure, any pretensions to novelty. They do not militate against the Newtonian system; and are presented to the reader more in the form of queries, than as doctrines fully established: they do not interfere with the elementary part of the work; or influence those conclusions that have been sanctified by time and experience. Whether I am right or wrong in my ideas of them, I doubt not but they will have a fair and candid reading. The theory was not sought, but has obtruded itself through an experience of near forty years: and though it differs in many points from the late received and adopted system of chemistry, my admiration of that simple and elegant system is not at all diminished; I rather lament that its worthy and ingenious founder [Lavoisier] did not live to have perfected so excellent and promising a beginning.”

A 1796 portrait (Ѻ) of what seems to be Walker (or possibly Joseph Priestley) giving one of his chemistry lectures.

“I feel a diffidence in the following explanations, conscious how much I am obliged to deviate from the received, or rather the new, documents of chemistry. For being able to find little difference between the phlogiston of the old chemists, and the caloric of the new, I have made the word fire to answer both.

Phlogiston was considered as fire united to some unknown substance. Lavoisier says, caloric is that exquisitely elastic fluid which produces heat. Am I excused in calling these plain fire, as it is generally produced on the earth, is known to be impure, and united with much terrestrial matter; and, therefore, may have given rise to the idea of an unknown substance being united to the simple element. This element of fire having its chemical affinities in common with grosser bodies, enters more abundantly into some than into others; hence some bodies are more combustible than others, from containing more quiescent or latent fire; and therefore when that fire is extricated from such bodies, it brings much of their gross matter along with it. But when fire is united with the volatile and finer parts of terrestrial matter, it transforms it into that thin fluid we call our atmosphere. Fire therefore assumes various appearances, and produces various effects; but still I conceive the element to be identical, simple, unchangeable, deriving its various character from the substances with which it is combined. In short, in its elementary state I conceive it to be electricity, and I hope to prove that electricity is derived from the sun.”

“AFFINITIVE ATTRACTION. Purposing to carry forward the mechanical and chemical philosophy hand in hand, this lecture is devoted to the first principles of the most extensive and useful branch of natural philosophy: for all arts and manufactures are little more than the composition, or decomposition, of the natural bodies of the earth. We are indebted for many of the important facts in chemical analysis to a race of visionaries, who, in the pursuit of the philosopher's stone, and the elixir vitae, happily stumbled upon a variety of discoveries, that have been of more importance to mankind, than the grand secrets they were in pursuit of would, had they been found out. These facts, though now systemized into a tolerably regular and consistent theory, simple in its principles, and, seemingly, accordant in its various ramifications; yet, I am sorry to say, it does not quite agree with the experiments and observations that have fallen in my way to make.

I think the grand basis of chemistry is attraction and repulsion. By attraction, I mean not only that of cohesion and gravitation (formerly explained), but the affinities of matter; the elective attractions, or local affections of it, that is, the tendency which the constituent parts of bodies have to unite readily with some substances, in preference, as it were, to all other parts of matter. Water and spirits are said to have an affinity, because they unite with the utmost readiness and affection. Water and oil have no affinity, because they will not unite (except by the intervention of an alkali, by which they become soap); for if oil and water are shaken together, it will be found the parts of each attract those of the same kind more strongly than the other, and the two presently separate. Acids and alkalis have so strong an affinity, that they rush into union with effervescence and ebullition so strong, indeed, is the attachment between acids and alkalis, that one will detach the other from most compounds with which that other is united.

The sea is a compound of fresh water and salt; yet so perfectly clear and homogeneous (as solutions generally are), that water and salt may be said to have affinity. That this selection, this choice, as it were, is but a modification of the attraction of cohesion, I entertain no doubt; for as various effects in chemical experiments prove the particles of matter to be of various shapes or forms, such particles as by their figure can lie conveniently by the fides of each other, or admit their centers coming nearer together, will adhere more strongly than those combinations where the corners and edges of particles do not fit, but enclose great spaces or interstices among them. This last may be called the attraction of cohesion; the other the attraction of affinity; but it is a distinction with little difference. See Plate V. in Magnetism, where the conforming fides of differently shaped particles so adjust themselves to one another as to become regular figures: something like the irregular flat stones in the Flaminian pavement that make a regular highway.”

“Because the laws of this, and the other species of cohesive attraction, do not seem to follow the laws of gravity (by diminishing as the squares of the distances increase), some imagine them of a distinct and different nature from the attraction that holds, the earth and the planets together. But can such small masses as we can make our experiments upon, betray the fame strong phenomena as a world, a planet, or a sun? Could we measure the ratio of the attraction, exhibited between two corks running to meet each other, when swimming on the surface of water, I entertain little doubt but it would be found to be in the same ratio as the laws of gravitation. Magnetic and electric attraction probably are the fame also. Similar phenomena must arise from the same law, if we are not to multiply causes; which certainly is a most excellent rule in philosophizing, or examining nature.”

“Objections are also made to fire and light being the same, because heated iron exhibits no light till it becomes violently heated. Fire lying in a latent state in metals, must be strongly excited by external heat, before it will betray signs of activity, or sensible light; for metals have so strong an affinity to fire, and retain it with so strong an attraction, that they must be attacked with great violence by external fire, or force, before they will part with their own.”

“Affinities are not confined to the grosser bodies of the chemists; they exist through all nature. Electricity, light, fire, air, water, &c. have all a tendency to unite with some bodies in preference to others. We fee, then, that one substance will dislodge another, where greater affinity takes place; and that we can make tables of the relationship which one kind of matter has to another, and thereby know the results of most kinds of mixtures beforehand. For if a fixed alkaline salt be united with vegetable acid, as vinegar, and formed into a neutral salt; on adding to this compound some marine acid, the acetous acid (vinegar) will be disengaged, so as to fly off in a moderate heat, leaving the marine acid in possession of the alkali: if then the nitrous acid be added, it will, in like manner, dispossess the marine, which will rife in white fumes ; though, without such an addition, it could not be detached from the alkali by any degree of heat: but on the addition of the vitriolic acid, the nitrous-gives way in its turn, exhaling in red fumes, leaving the last acid in full possession of the original alkali.”

Walker's 1802 affinity table, from his lecture four "On Chemistry", which would have been the affinity table that young Percy Shelley learned.

“The misery of the elective-affinity scheme is that men are not chemical substances [compare: people are not molecules], and that in nine cases in ten the force of the attraction works more constantly and lastingly upon the woman than the man. There is no stronger argument against it than the Memoirs of Mary Wollstonecraft (1798) (Ѻ). The Mormon polygamy is nothing more than a plant from the same evil seed sown in a baser soil, and is an attempt to compromise between the higher instincts of mankind, organized in their institutions, and the bestial propensities of sensualized individuals.”

“Adam Walker [1731-1821] British author and inventor. Taken from school "almost before he could read," Walker was largely self-educated. His dedication to learning earned him a reputation as a diligent student and as a result he was made an Usher at the Ledsham School and later was appointed writing master at Macclesfield. Encouraged by the success of his lectures, Walker began to tour, lecturing on natural philosophy in all the major cities. In 1778 he met Joseph Priestley who induced him to lecture at the Haymarket. As a result he was engaged as a lecturer at Eton College and several of the other public schools. He occupied his leisure time by perfecting various mechanical inventions including; an engine for raising water; steam carriages, rotary lights for the Scilly Isles (which were installed in 1790); a method of thermos-ventilation lines to heat homes without means of a kitchen fire, etc. Walker published several works the above was first published in 1799. System of Familiar Philosophy covers a wide range of topics; he illustrates Watts new patent steam engine along with a steam engine of his own invention; an early fire extinguisher. He also discusses electricity and magnetism in several of his lectures.”