they themselves difcover the errors into which they lead. But whereas the errors lie immediately before us, the indications of them are to be fought at a great dif

'tance.'

The Senfes are subject to a twofold defect. They either defert, or elfe deceive, us. Many fubjects elude their cognizance, however well they may be difpofed and 'free from impediment, either from the tenacity of the whole object, or the extreme

• Air and Fire are bodies of the most universal extent and operation in the material system. And the great Boerhaave speaking of the latter makes the following obfervation. So great is the power, so extensive the action,

and fo wonderful the manner wherein Fire acts, that it ' was anciently held and adored as the fupreme God by a 'nation reputed the wifeft of all others. Thus fome of the 'chemists, having found its extraordinary force, took it for an uncreated being, and many of the most eminent among ' them attributing all the knowledge they had acquired to this Inftrument, called themfelves Philofophers of Fire, as "thinking they could not be dignified by an higher title. 'There is however nothing more wonderful in the nature of Fire, than that whilft it is the chief cause and principle of almost all the effects cognizable by our fenfes, itself is IMPERCEPTIBLE by any fenfe, being fo incom'prehenfible, by reason of its extreme minuteness, that it eludes our nicest research; fo that with many it paffes for a spirit rather than a body.' Boerhaave's Chemistry.

• minute

'minutenefs of its parts, from the distance. ' of its fituation, the flowness or the velocity of its motion, its familiarity to the

eye, and from many other caufes. And again, where they fully apprehend their 'object, they are not to be fecurely relied upon; for the teftimony and information of

the Senfes depend on the analogy and con'ftitution of man, and not on thofe of the 'universe fo that, to fay that Senfe is the adequate measure or competent judge of things, is an affertion founded in miftake.

To obviate the imperfections of Sense phi'lofophers are under the neceffity, by much 'labour and attention, of calling in aid and 'affistance from every quarter, in order to 'fupply the deficiency, where the Senses fail 'us; and also to regulate and rectify them, 'where they vary in themselves. This is ' effected not so much by the use of Inftruments, as by the help of Experiments. For Experiments are much more penetrating and fubtle than the Senfes even when affifted by Inftruments of the most • exquifite

I 2

exquifite contrivance: I mean fuch Experi⚫ments as are ingeniously invented, and applied with skill and address to the elucidation of the very thing which is the subject of enquiry. Philofophers do not, there'fore, rely on the perception of the Senses immediately applied, as in their proper and ' common exercise, but bring the matter of judging to this iffue, that the Senfes judge of Experiments and Experiments of Things. Thus Experiments are, in fact, as the religious guardians of the Senfes, from which every thing in found philofophy is originally derived, and the skilful interpreters of their oracles; fo that, whilft others only pretend, true philofophers in 'reality cultivate and fupport, the Evi'DENCE OF SENSE.'

SECT.

SECT. II.

Of Phyfical REASONING.

Y fuch Experiments and Obfervations in

BY

aid of the External Senfes fkilfully chofen, artfully conducted, and judiciously applied, the philofopher advances from one ftage of enquiry to another,' by a flow but steady pace, in the rational investigation of the general Causes of Phyfical truth.

That one great and univerfal MIND who, made all things by his Power and preferves them in his Goodness, is the first and only Cause, operating at all times and in all places,

'Nonnulli qui experientia undis fe commifere fere mechanici facti funt; tamen in ipfa experientia erraticam quandam inquifitionem exercent, nec ei certa lege militant: Quin et plerique pufilla quædam penfa fibi propofuere, pro magno ducentes, fi unum aliquod inventum eruere poffint; inftituto non minus tenui, quam imperito. Nemo enim rei alicujus naturam, in ipfa re, recte aut feliciter perfcrutatur; verum poft laboriofam experimentorum variationem, non acquiefcit, fed invenit quod ulterius quærat. Baconus De Augm. Sc. Præf,

and

and producing, by an exertion of his will, all the various phænomena of the material fyftem. This firft and univerfal Caufe, however, in the ordinary administration of his providence, hath condefcended to employ Second Caufes as the inftruments of his will by which he acts; which second Causes he hath alfo appointed, in his Wisdom, to operate, through every part of his creation, by general Laws: And to trace the hand of the Almighty through all his works, to inveftigate these general Caufes and to erect them into the Laws of Phyfics, is the fublime, the delectable, and honourable employment of the Natural Philofopher."

From different Experiments and Obfervations made on the fame individual fubject, and from the fame Experiments and Obfervations made on different fubjects of the fame kind, by comparing and judging he discovers fome Qualities, Caufes, or Phænomena, which,

Newtonus philofophis præcepit, ut a Phænominis et Experimentis ad eorum Caufas progrediatur; atque inde ad Caufarum iftarum Caufas, et fic deinceps, donec ad Primam Causam perveniatur. Hoffley in Edit. Newt. Op. P. 495.

after