HARTSOKKER, NICOLAa 



IfAUVKY. WILLIAM. 



was UM ton of a oUntyman of Armley in Yorkshire. Havin* len 

 6r' frluoaUd at a print* Khuol, tin entered, at fifteen year* of age, 

 at Jewu College, CamMdgr, and beoama in time a Fellow of that 

 Scruple*, which would not allow him to subscribe the Thirty- 

 tides, prevented him frou afterwards entering the C'buroh, a* 

 oruinally intended, and he applied himself to the medical 

 L In tbi* profeeaion he practiced with sucoata, and attained 

 to annaMarahli emioeno*. 



He commenced th composition of the work by mean* of which he 

 has become universally known the ' Obeerrationi on Han, liu Frame, 

 his Duty, and hi* Expectation* ' at the age of twenty-five. It h>d 

 been the mibjeot of hu thought* even previously to this. He tell* 

 the world in hi* preface, that the fundamental idea of the work, the 

 possibility of explaining all state* of mind by association, was first 

 Mmatad to him by Mr. Qay* admirable Essay on the Fundamental 

 Principle of Virtue or Morality,' prefixed to Law'* translation of 

 Archbishop King'* 'Origin of Evil.' Although begun BO early aa 

 1730, the work was not finished until sixteen years after, and it was 

 ultimately published in 1748. 



Dr. Hartley was twice married, and bad children by both marriages. 

 He practised medicine successively at Newark, Bury St. Edmunds, in 

 London, and at Bath, where he died on the 25th of August 1757, at 

 the age of fifty-two year*. 



Combining as lie did with hU profession the pursuit of learning, 

 Dr. Hartley enjoyed through life the friendship of many distinguished 

 literary men of his time. Among these may be mentioned Bishops 

 Law, Butler, Warburton, and HoadUy, Dr. Jortin, Younz the poet, 

 and Hooke tha Kutuau historian. One of his children thus writes 

 concerning the qualities of mind and heart which endeared Dr. Hartley 

 to his private friends : " Hi* thoughts were not immersed in worldly 

 pursuit* or contentions, and therefore his life was not eventful or 

 turbulent, but placid and undisturbed by passion or violent ambition. 

 From hi* earliest youth his mental ambition was pro occupied by 

 pursuit* of science. His hour* of amusement were likewise bestowed 

 upon object* of taste and sentiment. Music, poetry, and history were 

 his favourite recreations. His imagination was fertile and correct; 

 his language and expression fluent and forcible. His natural temper 



K*J, cheerful, and sociable The virtuous principles 



which ore iumilled in his works were the invariable and decided prin- 

 ciples of his life and conduct" 



The chief end and great achievement of Hartley's great meta- 

 physical work is the application of the principles of association to 

 all our states of mind, or, as he himself calls them, not perhaps very 

 happily, " our intellectual pleasures and pains." But before proceed- 

 ing to eet forth and apply the principle of association, he attempts to 

 explain physically sensations and ideas, which he resolves into vibra- 

 tions of the medullary substance. The first bints of this his doctrine 

 of vibration* were derived, he tells us, from Sir Isaac Newton ; but, 

 whil- such speculations as these do not properly belong to the province 

 of the psychologist, it is obvious that they can never rest upon any 

 better foundation than conjecture. The commencement therefore of 

 Hartley's work detract* from rather than enhances its value. But 

 the doctrine of vibrations being dismissed, the principle of association, 

 of which little more than hinttt had previously been given by Hobbes 

 and Locke, is explained and applied by Hartley with a fullness and 

 acuteness which will ever render the work valuable. The second 

 part of the work is wholly occupied with natural and revealed 

 religion. 



HARTSOEKER, NICOLAS, a Dutch natural philosopher, -was born 

 atQoudain 1656: his father, who was a minister of the Reformed 

 religion, intended that he should enter the Church as a profession ; 

 bat a taste for the sciences, which the youth early evinced, prevented 

 this intention from being carried into effect. From the money which 

 was allowed him by his father, young Hartaoeker saved money enough 

 to pay the fee* of a teacher of mathematics; and be passed the 

 greater part of each night in studying the subjects connected with the 

 instruction which he received by day. 



An accidental circumstance is mid to have directed his attention to 

 the eonitruction of optical instrument* : having presented a filament 

 at glut to the flame of a candle, he was surprised to oUerve that the 

 extremity, when melted, tusumed a spherical form ; and he itnme- I 

 diaUly conceived the idea of using such sphere* as object-glasses for ' 

 microscope*. In an account which he published in 1078 of the instru- 

 ments thu* formed, he asa-rU that he discovered the animalcules 

 which exist in animal fluid* (LEOW*nuoCK] ; and, with the like 

 instrument*, Latorre is said to have first perceived the red globule. 



In 1674 Hartaoeker was tent to pursue hi* theological rtudie. at 

 Ley den j and in that city he became known to Huyghena. who encou- 

 raged him in the prosecution of hi* microscopical observation*. The 

 two philosopher* subsequently went together to P.ris. where Harl- 

 orkor was introduced to Cnssini, who recommended him U exercise 

 hi* ingenuity in the formation of object^ UMMI for telemopM ; and it 

 appears that, afUr several frilMeM sy*, be .uoceeded in ..l.Uinim; 

 MOM which were *uperior to any that bad been before executed. These 

 were of about 800 feet focal length ; and in order that thy might 

 have truly spherical formn, be fir*t, by means of and, made a very 

 aballow excavation in a plate ofgla**; then giving, by the like meat)., 



a slight convexity to on* aide of the pUU of which the intended 

 object-glad was to be formed, be placed the convex aide of the Utter 

 in the oavity of the other, and by friction brought the contiguous 

 surface* of both plates to equal and oontequnutly spherical figun a. 

 In 1694 he published his ' Ka*ai de Dioptrique,' 4to, Paris, in which, 

 bside treating of the science, he attempted to give a general theory 

 of the laws of nature respecting the hardneas, elasticity, transparency, 

 &o., of bodies. These subject* were afterwards explained in detail in 

 hi* ' Principe* de Physique,' which he published in 1696. The work 

 wa* criticised by a writer in the ' Journal de* Savans ' in the same 

 year, and Hartaoeker seems to have revenged himself by makin; a 

 violent attack on the ' Memoire* de 1'Acaddmie de* Sciences.' The 

 attack however remained unnoticed. It appear* to have been the 

 character of Hartaoeker to aeek occasions of entering into discussion* 

 with his friends; and he at length lost the good opinion of the patient 

 Leuwenhoeck by urging captious objections to the result* of some of 

 his experiments. 



Having become embarrassed in his circumstances. Hartaoeker was 

 obliged, in 1396, to quit Paris. He retired to Rotterdam, where he 

 published the work above mentioned ; and he afterwards removed to 

 Amsterdam. At this time be was introduced to the Czar Peter, then 

 travelling incognito, and he was appointed to give the monarch leg-ions 

 in mathematics. His conversation was so agreeable to the czar that 

 the hitter invited him to Russia. HarUoeker however declined leaving 

 Amsterdam, and the magistrates of the city built for him an observa- 

 torv in one of tbo bastions. 



The elector palatine having repoatedly offered Hnrtsoeker the place 

 of professor of mathematics and philosophy at Diisseldorf, he at length 

 accepted it, and in the year 1 7U4 he weut to reside in that city. V. hile 

 he held this post he made several journeys to different parts of Ger- 

 many in order to visit the learned men of the country; and at Hanover 

 he was presented to the elector by the celebrated Leibnitz. On his 

 return to Diisseldorf he caused three burning-lenses similar to those of 

 Tschirnhauseu to be executed. On the death of the elector palatine, 

 HarUoeker, declining the solicitation of the landgrave of Hcsse-Casse! 

 that he would reside in that city, retired to Utrecht, where he died in 

 1725. He had been admitted a foreign associate of the Academic del 

 Sciences of Paris in 1699; and he was also a member of the Academy 

 of Berlin. 



Hartaoeker U said to have entertained at one time an opinion that 

 there existed in every animal a plastic soul which was charged with 

 the preservation and development of the individual. He ia i-aiu to 

 have maintained also, and the opinion was probably founded on a 

 more refined idea expressed by Plato in the Timaeus, that from the 

 divinity descended a succession of intelligent beiuga, the lower orders 

 of which directed and preserved the universe; hu had moreover some 

 wild notions respecting an empire which he imagined to exist iu the 

 interior of the moon. 



In 1722 HarUoeker published a work entitled ' Recueil de plusieur* 

 Pieces de Physique, oil Ton fait principalement voir 1'luvalidiuS du 

 Systeme de Newton.' He also caused a letter to be printed in 

 the 'Journal des Savans,' containing some absurd remarks on the 

 hypothesis of the English philosopher. He treated Leibnitz no 

 better, attacking with great violence his system of ' monads ' and of 

 a ' pre-eatablighed harmony.' He would never admit the advantage* 

 of the ' Infinitesimal Calculus,' and persisted in considering it as an 

 unintelligible jargon by the aid of which certain learned men sought 

 to increase their reputation. He is characterised by J. Bernoulli as a 

 superficial and an arrogant man ; but his violence is supposed to be 

 less owing to envy than to a morbid taste for dispute. 



HARUN-AL-RASHID. [ABBiSims.l 



HARVEY, WILLIAM, wan born at Folkstone on the 1st of April 

 1578, and after having been some years at the grammar-school of 

 Canterbury, mas admitted at Caius College, Cambridge, in 1593, being 

 then in his sixteenth year. Having devoted himself to the study of 

 logic and natural philosophy for six years in that university, he removed 

 to Padua, at that time a celebrated school of medicine, where he 

 attended the lectures of Fabriciu* ab Aquapendeute on anatomy, of 

 Minadons on pharmacy, and of Casserius on surgery. He was admitted 

 doctor of medicine there, and returned home at the age of twenty-four. 

 At thirty he was elected Fellow of the College of Physicians, and 

 shortly after appointed physician to St. Bartholomew'* Hospital On 

 the 4th of August 1615, he was chosen by the college to deliver the 

 Lumleian lecture* on anatomy and surgery, and upon this occasion he 

 U supposed to have first brought forward hi* views upon the circu- 

 lation of the blood, which he afterward* more fully established, and 

 published in 1628. 



The importance of this great discovery was such, that it will be 

 necessary to investigate from the writing* of the author the steps by 

 which it was attained. We are informed by Boyle iu his ' Treatise on 

 Final Caute*,' that in the only conversation which he ever had with 

 Harvey, ha was told by him that the idea of the circulation wan 

 suggested to him by the consideration of the obvious use of tha 

 valve* of the vein*, which art) so constructed as to impede the course 

 of the blood from the heart through thorn vessels, while they |<i -mil, 

 it to pa** through them to the heart Before the tiuiu of Harvey the 

 opinions on the circulation were numerous and inconsistent. The blood 

 was supposed to be distributed to the various parts of the body by 



