John Playfair: Difference between revisions

From Citizendium
Jump to navigation Jump to search
imported>Gareth Leng
(New page: {{subpages}} ''(Text imported from [http://www.1911encyclopedia.org/John_Playfair Britannica 1911)'' JOHN PLAYFAIR (1748-1819), Scottish mathematician and physicist, was born at Benvie,...)
 
imported>Gareth Leng
(14 intermediate revisions by the same user not shown)
Line 1: Line 1:
{{subpages}}
{{subpages}}
'''John Playfair''' (1748-1819), mathematician and physicist, was born on the 10th of March 1748 at Benvie, Forfarshire, in [[Scotland]] where his father was the parish minister. He was taught at home until he was fourteen, when he entered the [[University of St Andrews]]. In 1766, when only eighteen, he applied for the chair of [[mathematics]] at [[Marischal College, Aberdeen]], but was unsuccessful. Six years later he applied for the chair of natural philosophy in St Andrews, again without success, and in 1773 he accepted the living of the united parishes of Liff and Benvie, which had become vacant on the death of his father. He continued, however, to carry on his mathematical studies, and in 1782 he resigned to become the tutor of [[Ferguson of Raith]]. This enabled him to be frequently in [[Edinburgh]], and to join the literary and scientific circles of the [[Scottish Enlightenment]], for which it was then famous. Moreover, through Maskelyne, the astronomer royal, who he had met in 1774, (during the 'Schiehallion experiments' to illustrate the principles of gravitation, from the effect of mountains in disturbing the plumb line) he also gained access to the scientific circles of London.
<blockquote>I met with a very cordial reception from him (Dr Maskelyne), and found that an acquaintance contracted among wilds and mountains is much more likely to be durable than one made up in the bustle of a great city: nor would I, by living in London for many years, have become so well acquainted with this astronomer, as I did by partaking of his hardships and labours on Schehallien for a few days.</blockquote>


''(Text imported from [http://www.1911encyclopedia.org/John_Playfair Britannica 1911)''
==Life==
In 1785, [[Adam Ferguson]] exchanged the moral chair in the [[University of Edinburgh]] for that of mathematics, taught by professor [[Dugald Stewart]], and, being in poor health, chose Playfair as his assistant. Playfair continued, however, to attend his two pupils until 1787, when he moved in with his mother, who had lived in Edinburgh for some time. He now began a series of papers which appeared in the ''Transactions of the Royal Society of Edinburgh''. The first was the life of Dr Matthew Stewart, the late professor of mathematics in the University of Edinburgh. A second was on the causes which affect the accuracy of Barometrical Measurements. A third was ''Remarks on the Astronomy of the Brahmins''.


In 1795, he published an edition of [[Euclid]]’s ''Elements'' for the use of his class. In this work, he adopted the plan of using algebraic signs instead of words, and "Playfair’s Euclid" became well known in most mathematical schools. In 1797 he suffered a severe attack of rheumatism, during which he sketched an essay on the accidental discoveries which have been made by men of science whilst in pursuit of something else, or when they had no determinate object in view; and wrote the observations on the trigonometrical tables of the Brahmins, and the theorems relating to the figure of the earth, which were laterpublished in the ''Transactions of the Royal Society of Edinburgh''.


JOHN PLAYFAIR (1748-1819), Scottish mathematician and physicist, was born at Benvie, Forfarshire, where his father was parish minister, on the 10th of March 1748. He was educated at home until the age of fourteen, when he entered the university of St Andrews. In 1766, when only eighteen, he was candidate for the chair of mathematics in Marischal College, Aberdeen, and, although he was unsuccessful, his claims were admitted to be high. Six years later he made application for the chair of natural philosophy in his own university, but again without success, and in 1773 he was offered and accepted the living of the united parishes of Liff and Benvie, vacant by the death of his father. He continued, however, to carry on his mathematical and physical studies, and in 1782 he resigned his charge in order to become the tutor of Ferguson of Raith. By this arrangement he was able to be frequently in Edinburgh, and to cultivate the literary and scientific society for which it was at that time specially distinguished; and through Maskelyne, whose acquaintance he had first made in the course of the celebrated Schiehallion experiments in 1774, he also gained access to the scientific circles of London. In 1785 when Dugald Stewart succeeded Ferguson in the Edinburgh chair of moral philosophy, Playfair succeeded the former in that of mathematics. In 1802 he published his celebrated volume entitled Illustrations of the Huttonian Theory of the Earth. To its publication the influence exerted by James Hutton on the progress of geological knowledge is largely due. In 1805 he exchanged the chair of mathematics for that of natural philosophy in succession to Dr John Robison, whom also he succeeded as general secretary to the Royal Society of Edinburgh. He took a prominent part, on the Liberal side, in the ecclesiastical controversy which arose in connexion with Leslie's appointment to the post he had vacated, and published a satirical Letter (1806) which was greatly admired by his friends. He was elected F.R.S. in 1807. He died in Edinburgh on the 20th of July 1819.  
About the same time, his friend [[James Hutton]] died, and Playfair, who intended to have written his memoir, found in the study of his works, a vast field. Playfair today is remembered not for his contributions to mathematics, but for the role that he played in bringing the work of Hutton to prominence.


A collected edition of Playfair's works, with a memoir by James G. Playfair, appeared at Edinburgh in 4 vols. 8vo. His writings include a number of essays contributed to the Edinburgh Review from 1804 onwards, various papers in the Phil. Trans. (including his earliest publication, "On the Arithmetic of Impossible Quantities," 1779, and an "Account of the Lithological Survey of Schehallion," 1811) and in the Transactions of the Royal Society of Edinburgh ("On the Causes which affect the Accuracy of Barometrical Measurements," &c.), also the articles "Aepinus" and "Physical Astronomy," and a "Dissertation on the Progress of Mathematical and Physical Science since the Revival of Learning in Europe," in the Encyclopaedia Britannica (Supplement to fourth, fifth and sixth editions). His Elements of Geometry first appeared in 1795 and have passed through many editions; his Outlines of Natural Philosophy (2 vols., 1812-1816) consist of the propositions and formulae which were the basis of his class lectures. Playfair's contributions to pure mathematics were not considerable, his paper "On the Arithmetic of Impossible Quantities," that "On the Causes which affect the Accuracy of Barometrical Measurements," and his Elements of Geometry, all already referred to, being the most important. His lives of Matthew Stewart, Hutton, Robison, many of his reviews, and above all his "Dissertation" are of the utmost value.
In 1802, Playfair published ''Illustrations of the Huttonian Theory of the Earth''. To its publication the influence exerted by Hutton on the progress of geological knowledge is largely due. In 1805, he exchanged the chair of mathematics for that of natural philosophy in succession to Dr John Robison, whom also he succeeded as general secretary to the Royal Society of Edinburgh. He took a prominent part, on the Liberal side, in the ecclesiastical controversy which arose in connexion with Leslie's appointment to the post he had vacated, and published a satirical letter (1806). He was elected a [[Fellow of the Royal Society]] in 1807. He died in Edinburgh on 20th July 1819.
 
==Illustrations of the Huttonian Theory of the Earth==
Playfair's "Illustrations of the Huttonian Theory of the Earth" expressed Hutton's evidence and conclusions in a crisp, tightly organised form, making it easy to follow the logic of the argument - and very hard to refute it lightly. A critical step in Hutton's case was his argument that [[granite]] was a rock formed under great heat and pressure which in places had been forced upwards to displace overlying strata, and occasionally to infiltrate those strata:
 
''"... in Dr. Hutton’s theory, granite is regarded as a stone of more recent formation that the strata incumbent on it; as a substance which has been melted by heat, and which, when forced up from the mineral regions, has elevated the strata at the same time."
 
Playfair laid out the observational facts simply and clearly
 
''"...It has been observed in many instances, that where granite and stratified rocks, such as primary schistus, are in contact, the latter are penetrated by veins of the former, which traverse them in various directions."''
 
He systematically dismantled the conventional view, that granite was formed by mixtures of minerals dissolved in water (and produced at the time of the supposed [[flood]])  
 
''"These phenomena, which were first distinctly observed by Dr. Hutton, are of great importance in geology, and afford a clear solution of the two chief questions concerning the relation between granite and schistus. As every vein must be of a date posterior to the body in which it is contained, it follows, that the schistus was not superimposed on the granite, after the formation of this last. If it be argued, that these veins, though posterior to the schisti, are also posterior to the granite, and were formed by the infiltration of water in which the granite was dissolved or suspended; it may be replied, [first], That the power of water to dissolve granite, is a postulatum of the same kind that we have so often, and for such good reason, refused to concede; and [second], That in many instances the veins proceed from the main body of the granite upwards into the schistus; so that they are in planes much elevated in respect of the horizon, and have a direction quite opposite to that which the hypothesis of infiltration requires.  It remains certain, therefore, that the whole mass of granite, and the veins proceeding from it, are coeval, and both of later formation than the strata."''
 
Thus his conclusions were direct and forensic.
 
''"the fluidity which preceded the consolidation of mineral substances was simple, that is, it did not arise from the combination of these substances with any solvent; and next, that after consolidation, these bodies have been raised up by an expansive force acting from below, and have by that means been brought into their present situation."''


==References==
==References==
<references/>
<references/>
*[http://www.electricscotland.com/history/other/playfair_john.htm Significant Scots John Playfair] Electricscotland.com
*[http://www.1911encyclopedia.org/John_Playfair John_Playfair] Encyclopedia Britannica 1911

Revision as of 14:39, 17 February 2011

This article is a stub and thus not approved.
Main Article
Discussion
Related Articles  [?]
Bibliography  [?]
External Links  [?]
Citable Version  [?]
 
This editable Main Article is under development and subject to a disclaimer.

John Playfair (1748-1819), mathematician and physicist, was born on the 10th of March 1748 at Benvie, Forfarshire, in Scotland where his father was the parish minister. He was taught at home until he was fourteen, when he entered the University of St Andrews. In 1766, when only eighteen, he applied for the chair of mathematics at Marischal College, Aberdeen, but was unsuccessful. Six years later he applied for the chair of natural philosophy in St Andrews, again without success, and in 1773 he accepted the living of the united parishes of Liff and Benvie, which had become vacant on the death of his father. He continued, however, to carry on his mathematical studies, and in 1782 he resigned to become the tutor of Ferguson of Raith. This enabled him to be frequently in Edinburgh, and to join the literary and scientific circles of the Scottish Enlightenment, for which it was then famous. Moreover, through Maskelyne, the astronomer royal, who he had met in 1774, (during the 'Schiehallion experiments' to illustrate the principles of gravitation, from the effect of mountains in disturbing the plumb line) he also gained access to the scientific circles of London.

I met with a very cordial reception from him (Dr Maskelyne), and found that an acquaintance contracted among wilds and mountains is much more likely to be durable than one made up in the bustle of a great city: nor would I, by living in London for many years, have become so well acquainted with this astronomer, as I did by partaking of his hardships and labours on Schehallien for a few days.

Life

In 1785, Adam Ferguson exchanged the moral chair in the University of Edinburgh for that of mathematics, taught by professor Dugald Stewart, and, being in poor health, chose Playfair as his assistant. Playfair continued, however, to attend his two pupils until 1787, when he moved in with his mother, who had lived in Edinburgh for some time. He now began a series of papers which appeared in the Transactions of the Royal Society of Edinburgh. The first was the life of Dr Matthew Stewart, the late professor of mathematics in the University of Edinburgh. A second was on the causes which affect the accuracy of Barometrical Measurements. A third was Remarks on the Astronomy of the Brahmins.

In 1795, he published an edition of Euclid’s Elements for the use of his class. In this work, he adopted the plan of using algebraic signs instead of words, and "Playfair’s Euclid" became well known in most mathematical schools. In 1797 he suffered a severe attack of rheumatism, during which he sketched an essay on the accidental discoveries which have been made by men of science whilst in pursuit of something else, or when they had no determinate object in view; and wrote the observations on the trigonometrical tables of the Brahmins, and the theorems relating to the figure of the earth, which were laterpublished in the Transactions of the Royal Society of Edinburgh.

About the same time, his friend James Hutton died, and Playfair, who intended to have written his memoir, found in the study of his works, a vast field. Playfair today is remembered not for his contributions to mathematics, but for the role that he played in bringing the work of Hutton to prominence.

In 1802, Playfair published Illustrations of the Huttonian Theory of the Earth. To its publication the influence exerted by Hutton on the progress of geological knowledge is largely due. In 1805, he exchanged the chair of mathematics for that of natural philosophy in succession to Dr John Robison, whom also he succeeded as general secretary to the Royal Society of Edinburgh. He took a prominent part, on the Liberal side, in the ecclesiastical controversy which arose in connexion with Leslie's appointment to the post he had vacated, and published a satirical letter (1806). He was elected a Fellow of the Royal Society in 1807. He died in Edinburgh on 20th July 1819.

Illustrations of the Huttonian Theory of the Earth

Playfair's "Illustrations of the Huttonian Theory of the Earth" expressed Hutton's evidence and conclusions in a crisp, tightly organised form, making it easy to follow the logic of the argument - and very hard to refute it lightly. A critical step in Hutton's case was his argument that granite was a rock formed under great heat and pressure which in places had been forced upwards to displace overlying strata, and occasionally to infiltrate those strata:

"... in Dr. Hutton’s theory, granite is regarded as a stone of more recent formation that the strata incumbent on it; as a substance which has been melted by heat, and which, when forced up from the mineral regions, has elevated the strata at the same time."

Playfair laid out the observational facts simply and clearly

"...It has been observed in many instances, that where granite and stratified rocks, such as primary schistus, are in contact, the latter are penetrated by veins of the former, which traverse them in various directions."

He systematically dismantled the conventional view, that granite was formed by mixtures of minerals dissolved in water (and produced at the time of the supposed flood)

"These phenomena, which were first distinctly observed by Dr. Hutton, are of great importance in geology, and afford a clear solution of the two chief questions concerning the relation between granite and schistus. As every vein must be of a date posterior to the body in which it is contained, it follows, that the schistus was not superimposed on the granite, after the formation of this last. If it be argued, that these veins, though posterior to the schisti, are also posterior to the granite, and were formed by the infiltration of water in which the granite was dissolved or suspended; it may be replied, [first], That the power of water to dissolve granite, is a postulatum of the same kind that we have so often, and for such good reason, refused to concede; and [second], That in many instances the veins proceed from the main body of the granite upwards into the schistus; so that they are in planes much elevated in respect of the horizon, and have a direction quite opposite to that which the hypothesis of infiltration requires. It remains certain, therefore, that the whole mass of granite, and the veins proceeding from it, are coeval, and both of later formation than the strata."

Thus his conclusions were direct and forensic.

"the fluidity which preceded the consolidation of mineral substances was simple, that is, it did not arise from the combination of these substances with any solvent; and next, that after consolidation, these bodies have been raised up by an expansive force acting from below, and have by that means been brought into their present situation."

References