BROWN, Robert.

A Brief Account of Microscopical Observations made in the Months of June, July, and August, 1827, on the Particles contained in the Pollen of Plants; and on the general Existence of active Molecules in organic and inorganic bodies. [With:] Additional remarks on active molecules.

Edinburgh; London: Adam Black; Longman, Rees, Orme, Brown & Green, 1828-1929.

First journal printing, in original never-bound sheets, of Robert Brown’s description of the molecular phenomenon later known as “Brownian motion,” one of the most important discoveries of the nineteenth century. It formed the basis for kinetic theory of gases and served as proof of the existence of atoms and molecules. “In 1827 Brown, while making microscopical observations, saw that pollen grains while suspended in liquid, engaged in a continuous, haphazard, zig-zag movement. The idea that gases and liquids consist of molecules in rapid motion was not new, but it had remained largely speculative until it was scientifically proved and investigated in detail by Robert Brown and his followers” (PMM). “While studying pollen, Brown observed particles within the grains in a state of constant motion. He extended his observations to both dead and inorganic matter and found that such motion was not restricted to live pollen but could be observed in any sub-stance ground fine enough to be suspended in water. In 1879 William Ramsay explained that Brownian motion is due to the impact of particles of the molecules in the surrounding fluid, an explanation proved in 1908 by Jean Perrin. Brown's observations also inspired Einstein's 1905 paper ‘Ueber die von der molekular-kinestisch Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendieren Teilchen’, which gave a theory of Brownian motion based on the kinetic theory of gases” (Norman). "Brown’s careful extended work dispelled the animist view of the construction of organic material. However, the true significance of what became known as Brownian Motion or movement was not realized until long afterwards by physicists and mathematicians. All these observations were made using simple microscopes. He demonstrated streaming to Charles Darwin who went to sit with him for training in microscopy and who much later was to build on Brown's pioneering work on pollination and fertilization. Brown, again using his simple microscopes, also helped James Paget to investigate trichinosis” (ODNB). The publication caused sufficient stir as to be mentioned in George Eliot’s Middlemarch (1872): “I have some sea-mice – fine specimens – in spirits. And I will throw in Robert Brown's new thing – Microscopic Observations on the Pollen of Plants – if you don’t happen to have it already” (Chapter XVII). The era of modern physics was in part inaugurated by Brown’s publication, and it has entirely permeated modern mathematics: probability theory, stochastic processes, chaos theory, random processes, fractals, etc. “Brownian motion continues to be of immeasurable importance in modern science, from physics through biology to the latest wonders of nanotechnology. Indeed, this is reflected in citation statistics, which show that Einstein’s papers on Brownian motion have been cited many more times than his publications on special relativity or the photoelectric effect” (‘Einstein’s random walk,’ Physics World, 15 January 2005).

“Brown was born in the coastal town of Montrose, north of Dundee, Scotland in 1773. The family moved to Edinburgh in 1790. Brown initially intended to study medicine at the University of Edinburgh, but soon fell in love with botany. He ventured into the Scottish Highlands, collecting plants and recording their descriptions in minute detail, and he discovered a new species of grass, Alopecurus alpinus. His studies were interrupted by his military service, and he found himself stationed in Ireland as surgeon’s mate – a position that left him with plenty of time to pursue his botanical interests.

“By the end of the century, Brown was well established as an amateur among the Irish community of botanists, even though he never completed a formal degree. But he had little hope of earning a living as a botanist, until he was selected to be the naturalist for a scientific expedition to explore ‘New Holland’ – the continent we now know as Australia. His instructions were to collect as many plant, insect, and bird specimens as possible. He set sail from London aboard the Investigator in July 1801 and stopped at the Cape of Good Hope several months later. Brown would later recall his two weeks there as “some of the pleasantest botanizing” he’d ever experienced. By December he had arrived in Western Australia, and he spent the next three and half years collecting 3400 specimens, some 2000 of them previously unknown species. Much of this collection was lost en route back to England, but there were still ample specimens for Brown to catalogue when he returned home in 1805.

“This effectively launched his illustrious career in botany, although he was just as interested in studying the physiology of plants as collecting and classifying them. That is how he became fascinated with the pollen particles from the plant species Clarkia pulchella floating in water under his microscope – an instrument that was still a bit of a scientific novelty. Within those grains of pollen, he noticed even smaller particles jiggling in seemingly random motions, as if they were alive” (APS News).

“The researches originated, Brown tells us, in an attempt to find the mode of action of pollen in the process of impregnation. The first plant examined was Clarkia pulchella, whose pollen contains particles varying from 1/4000th to 1/5000th of an inch in length.

‘While examining the form of these particles immersed in water, I observed many of them very evidently in motion; their motion consisting not only of a change of place in the fluid, manifested by alterations in their relative positions, but also not infrequently by a change of form of the particle itself.... In a few instances the particle was seen to turn on its longer axis. These motions were such as to satisfy me, after frequently repeated observation, that they arose neither from currents in the fluid, nor from its gradual evaporation, but belonged to the particle itself.’

“Brown then examined particles (or ‘Molecules’ as he now started to call them) from several other plants, not only living ones but also some that had been preserved in an herbarium for not less than a century. He observed similar movements in all cases. At this point he recorded rather recklessly his first guess about the origin of the motion:

‘Reflecting on all the facts with which I had now become acquainted, I was disposed to believe that the minute spherical particles or Molecules of apparently uniform size … were in reality the supposed constituent or elementary Molecules of organic bodies, first so considered by Buffon and Needham, then by Wrisberg with greater precision, and very recently by Dr. Milne Edwards, who has revived the doctrine... I now therefore expected to find these molecules in all organic bodies: and accordingly on examining the various animal and vegetable tissues, whether living or dead, they were always found to exist.... But after studying several mineralized vegetable remains, Brown began to suspect that moving molecules could also be obtained from inorganic sources. It turned out that practically every conceivable substance, from a piece of window glass to a fragment of the Sphinx, could be made to yield particles that moved in water.’

“Brown's memoir attracted considerable attention, and several other scientists reported observations of a similar kind. But there was almost universal condemnation of Brown, at least on the Continent, for what was thought to be his opinion that the molecules are self-animated. All kinds of physical explanations for the motion were suggested: unequal temperatures in the strongly illuminated evaporation, air currents, heat flow, capillarity, motions caused by the hands of the observer, and so forth.

“Michael Faraday gave a Friday evening lecture on Brownian movement at the Royal Institution on 21 February 1829, in which he defended Brown. According to Faraday, Brown's experiments were carefully done and sufficed to show that the movements could not be explained by any of the causes so far suggested. In fact, Brown had simply admitted that he could not account for the motions; but by using the term ‘molecule’ (which Faraday was careful to distinguish from ‘ultimate atoms’) Brown had laid himself open to misunderstanding, ‘because the subject connects itself so readily with general molecular philosophy that all think he must have meant this or that...’

“In a second memoir, ‘Additional remarks on active molecules,’ Brown replied to some of his critics and reported further experiments. He disclaimed the view that the molecules are animated, admitting that some readers may have misunderstood him because he had ‘communicated the facts in the same order in which they occurred, accompanied by the views which presented themselves in the different stages of the investigation.’ He now wished to prove that the motion of particles in a fluid cannot be due, as others had suggested, to ‘that intestine motion which may be supposed to accompany its evaporation.’ To accomplish this proof, he mixed water containing particles with almond-oil. After being shaken, the mixture contained drops of water ranging from 1/50th to 1/200th of an inch in diameter. Being surrounded by almond-oil, these drops of water do not evaporate for a considerable time. Some of the drops contained only a single particle. ‘But in all the drops thus formed and protected, the motion of the particles takes place with undiminished activity, while the principal causes assigned for that motion, namely, evaporation, and their mutual attraction and repulsion, are either materially reduced or absolutely null.’

“Brown was aware that the evaporation of liquids was considered by physicists to be somehow connected with ‘intestine motions,’ but he misunderstood the connection; he thought that if evaporation were suppressed by some external cause, then the intestine motion would also have to stop.

“The other cause of motion that Brown thought he had excluded by this experiment – mutual attraction or repulsion of the particles – was occasionally proposed later in the 19th century. No one seems to have noticed Brown’s refutation of this explanation: the fact that a single particle in a drop of water will exhibit the same motion as it does when other particles are present.

“In this second memoir, Brown also referred to the previous observations of Leeuwenhoek, Stephen Grant, Needham, Buffon, and Spallanzani, but he said that all these writers confused ‘Molecular’ motion with animalcular motion … By the 1870s, at least, it was becoming common for authors of books on the microscope to include warnings about Brownian movement, in case observers should mistake it for the motion of living beings and attempt to build fantastic theories on it …

“It may not be superfluous to quote the recollections of Charles Darwin from the 1830s:

‘I saw a good deal of Robert Brown, ‘facile Princeps Botanicorum,’ as he was called by Humboldt. He seemed to me to be chiefly remarkable for the minuteness of his observations and their perfect accuracy. His knowledge was extraordinarily great, and much died with him, owing to his excessive fear of ever making a mistake. He poured out his knowledge to me in the most unreserved manner, yet was strangely jealous on some points. I called on him two or three times before the voyage of the Beagle [1831], and on one occasion he asked me to look through a microscope and describe what I saw. This I did, and believe now that it was the marvelous currents of protoplasm in some vegetable cell. I then asked him what I had seen; but he answered me, ‘That is my little secret’’” (Brush, pp. 659-662).

There is no doubt that Brown recognised his motion as a fundamental phenomenon. However, he offered no explanation and did nothing quantitative, but he did carry out observations under controlled conditions and performed an experiment which eliminated many other possible causes, principally motion due to convection currents. Many who followed him were less careful and heated controversy ensued.

“Early explanations [of Brownian motion] attributed the motion to thermal convection currents in the fluid. When observation showed that nearby particles exhibited totally uncorrelated activity, however, this simple explanation was abandoned. By the 1860s theoretical physicists had become interested in Brownian motion and were searching for a consistent explanation of its various characteristics: a given particle appeared equally likely to move in any direction; further motion seemed totally unrelated to past motion; and the motion never stopped. An experiment (1865) in which a suspension was sealed in glass for a year showed that the Brownian motion persisted. More systematic investigation in 1889 determined that small particle size and low viscosity of the surrounding fluid resulted in faster motion.

“Since higher temperatures also led to more-rapid Brownian motion, in 1877 it was suggested that its cause lay in the ‘thermal molecular motion in the liquid environment.’ The idea that molecules of a liquid or gas are constantly in motion, colliding with each other and bouncing back and forth, is a prominent part of the kinetic theory of gases developed in the third quarter of the 19th century by the physicists James Clerk Maxwell, Ludwig Boltzmann, and Rudolf Clausius in explanation of heat phenomena. According to the theory, the temperature of a substance is proportional to the average kinetic energy with which the molecules of the substance are moving or vibrating. It was natural to guess that somehow this motion might be imparted to larger particles that could be observed under the microscope; if true, this would be the first directly observable effect that would corroborate the kinetic theory. This line of reasoning led the German physicist Albert Einstein in 1905 to produce his quantitative theory of Brownian motion. Similar studies were carried out on Brownian motion, independently and almost at the same time, by the Polish physicist Marian Smoluchowski, who used methods somewhat different from Einstein’s.

“Einstein wrote later that his major aim was to find facts that would guarantee as much as possible the existence of atoms of definite size. In the midst of this work, he discovered that according to atomic theory there would have to be an observable movement of suspended microscopic particles. Einstein did not realize that observations concerning the Brownian motion were already long familiar. Reasoning on the basis of statistical mechanics, he showed that for such a microscopic particle the random difference between the pressure of molecular bombardment on two opposite sides would cause it to constantly wobble back and forth. A smaller particle, a less viscous fluid, and a higher temperature would each increase the amount of motion one could expect to observe. Over a period of time, the particle would tend to drift from its starting point, and, on the basis of kinetic theory, it is possible to compute the probability of a particle’s moving a certain distance in any given direction during a certain time interval” (Britannica).

“It is of interest from the point of view of scientific method that the proper quantitative analysis of Brownian motion was not found for so long because the many able experimentalists following him were observing the wrong quantity. It was natural to observe the velocity of the particles but what one observed with the eye is not what the particle is actually doing owing to the limitations of the frequency response of the human optical system and is a rather subtle matter. Only when this is allowed for does one find from visual observations of Brownian motion that the root mean square velocity in one direction is as predicted by kinetic theory. Einstein’s vital contribution was to direct attention to the distance the particle moved – or, more precisely, the mean square distance” (Powles).

“The introduction of the ultramicroscope in 1903 aided quantitative studies by making visible small colloidal particles whose greater activity could be measured more easily. Several important measurements of this kind were made from 1905 to 1911. During this period the French physicist Jean-Baptiste Perrin was successful in verifying Einstein’s analysis, and for this work he was awarded the Nobel Prize for Physics in 1926. His work established the physical theory of Brownian motion and ended the skepticism about the existence of atoms and molecules as actual physical entities” (Britannica).

Brown’s ‘Brief Account’ was published essentially simultaneously in The Philosophical Magazine and in the Edinburgh New Philosophical Journal. No priority has been established: the paper appeared in the September 1828 issue of the Philosophical Magazine, which was published monthly, and in the July-September issue of the Edinburgh New Philosophical Journal, which was published quarterly. Both were preceded by the privately-printed issue (which does not of course include the ‘Additional remarks’). Brown sent a copy of the latter to his friend and fellow Scot Robert Jameson, founder and publisher of The Edinburgh New Philosophical Journal. As Jameson remarks in a footnote, ‘This important and highly interesting Memoir was sent us by our friend Mr. Brown, and, although not published, we believe we are not acting contrary to the wishes of the author in giving it an early place in the Edinburgh Philosophical Journal’. In the Philosophical Magazine version, the editor added a note ‘We have been favoured by the Author with permission to insert the following paper, which has just been printed for private distribution.’ The privately printed issue is exceptionally rare, with fewer than 20 copies known.

Dibner 156 (privately printed issue); Norman 353 (privately-printed issue); Norman 354 (Philosophical Magazine journal issue of the first paper only); Parkinson p. 284; PMM 290 (privately printed issue); Sparrow, Milestones of Science, 31 (Edinburgh New Philosophical Journal issue). Brush, The Kind of Motion We Call Heat, 1976. ‘August 1827: Robert Brown and Molecular Motion in a Pollen-filled Puddle,’ APS News, Vol. 25, No. 8, August 2016. Mabberley, Jupiter Botanicus: Robert Brown of the British Museum, 1985. Powles, ‘Brownian motion – June 1827,’ Physics Education 13 (1978), pp. 310-312.

8vo (228 × 145 mm). Two complete issues of The Philosophical Magazine, offered in their original, uncut, and never-bound sheets: Vol. IV, no. 21 (September 1828), pp. [161]–240, with 2 plates; and Vol. VI, no. 33 (September 1829), pp. [161]–240. Brown’s contributions occupy pp. 161–173 in the 1828 issue and pp. 161–166 in the 1829 issue.

Item #6573

Price: $12,500.00