SPRING. 



ing and alcertaining the nature, fituation, and direftion of 

 under-ground fprings and colledl'oiis of water, as well ar^ in 

 fome meafure, the nature and pofition of the different fub- 

 llrata in land, before the work of cutting and forming the 

 drains for taking off the injurious wetnefs is begun. It is 

 conftrufted of copper, in the pipe form, m a very neat, 

 fimple, and cheap manner, fo as to admit of being put down 

 into the ground in holes formed by the boring-auger ; and 

 by being made to be wrought as a pump, is capable of 

 fliewing the prefence of water, where the pred'ure of it in 

 the higher grounds above is not fufficient to force it up 

 through the auger-holes, which is the cafe in many inftances. 

 The nature and direftioii of the under-ltrata are, in fome 

 degree, found in boring and putting the pump down through 

 them. It is the invention and difcovery of Mr. Wakefield, 

 who has been long much engaged in the praftice of drain- 

 ing in feveral different places and parts of the kingdom. See 

 SPRlUG-Drainitig. 



This is a contrivance which, with the boring-rod, would 

 feem to be capable of being of very great importance in 

 the bufinefs of Ipring-draining, as tending, by the facility 

 and certainty which it affords of difcovering and pointing 

 out the nature, exiftence, and lines of fprings, before any 

 thing is done, to prevent a great deal of unneceffary labour 

 in cutting at random, as has hitherto moftly been the cafe, 

 and thereby fave much ufelefs expence to thofe who are 

 under the neceffity of having fuch works performed. The 

 utility of chefe contrivances is more fully fhewn under 

 the head alluded to above. 



SemtiG-Draining Bricks, the feveral different kinds, forms, 

 and (hapes of bricks which are contrived for this ufe, and 

 which differ from thofe of the common fort employed 

 in building purpofes. They are of many different defcrip- 

 tions. Thefe kinds of bricks are moftly well calculated for 

 forming drains which are to carry off the water coming 

 from fprings, as a large extent of land may often be ren- 

 dered dry by no very great quantity of fuch materials ; but 

 they are not fo well fuited for drains which are to remove 

 water which Itagnates on the furface of land, though they 

 are occafionally made ufe of for that purpofe. They fome- 

 times form hollow paffages for the water to run along, as in 

 ftiff foils ; but in fuch as are foft they are made to form a 

 fort of pipe or cylindrical paffage for the fame, by being 

 laid one upon the other. See SpRiNG-Z)rain. 



SpRrNG-jB<jf, a term applied to that fort of bog or 

 boggy wetnefs which is caufed by fprings, in contradif- 

 tinftion to that, or the fwampy wetnefs, which proceeds 

 from the ftagnation of rain or other water upon the furface 

 of land where thefe prevail in land-locked fituations. 



Springbogs are, for the moil part, more confined than 

 thofe of the contrary kind, but they are fometimes equally 

 extenfive with them. 



^VRisa-Brlnc. See SALT-Brine Spring. 



Spring, Elater, in Phyfus, denotes a natural faculty, op 

 endeavour, of certain bodies to return to their firft itate, 

 after having been violently put out of the fame by com- 

 preffing, bending them, or the like. 



This faculty philofophers ufually call elajiic force, or 

 elcylicity. 



Fkas only jump to excefllve heights by means of a 

 fpringy membrane, eafily vifible by a microfcope ; and of 

 which we liave a curious figure in Dr. Hooke's Micro- 

 graphia. By the elaltic force of this fpring they are en- 

 abled to leap two hundred times the height of their own 

 body. See Fj.f.a. 



Nature has provided for the regular fowing of the feeds 

 ai feveral kinds of plants, by furnilhing them with a fpring, 



which is wound fometimes round the outfide, and fometimes 

 round the mfide of the cafe in which the feeds are contained. 

 See Semination. 



Spring, in Mechanics, is any elaftic body, commonly of 

 fteel properly tempered, and formed in various ways, ac- 

 cording to the purpofe it is intended to anfwer, whether it 

 be for giving motion to a machine, or for equalizing and 

 modifying motion derived from fome other agent. Springj 

 are alfo introduced into inftrumeats, called fpring fteel- 

 yards, for afcertaining the weights of bodies, as well as 

 having various other applications, which it would be ufe- 

 lefs to enumerate in this place. 



Confidering, therefo.-e, the numerous ufes to which this 

 kind of force may be dirc£led, it muft appear very remark- 

 able that fo little is known of the true principle of the 

 adion of fprings, and of the laws by which their powers 

 are regulated ; we know, indeed, of no regular fet of ex- 

 periments, that have yet been made, which are at all ade- 

 quate to reducing their operation to correft mathematical 

 principles. 



Dr. Hooke feems to have been the firft writer who un- 

 dertook experiments on the aftion of fprings, with a view 

 of drawing from them general conclufions, and by this 

 means to introduce them into the theory of rational mecha- 

 nics : and the refult which he thus obtained, was his cele- 

 brated law *' ut tenfio fie vis," the tenfion is as the force : 

 a law which fome fubfequent experimenters have ftated to 

 be correift, while others of confiderable eminence have de- 

 nied its accuracy and agreement with experiment in nume- 

 rous cafes. The fad, therefore, feems to be, that in 

 fprings of a certain form, and ivithin certain limits, the prin- 

 ciple is juft ; but that others of different form, and in all, 

 when the force is very confiderable in regard to the ftrength 

 of the fpring, it does not apply : and, confequeatly, that 

 much ftill remains to be done before the aftions of different 

 fprings can be admitted to form a part of theoretical me- 

 chanics. 



Dr. Jurin, by adopting the principle above referred to, 

 viz.. " the tenfion is as the force," fucceeded in rendering 

 the adion of fprings fufceptible of mathematical computa- 

 tion. See Phil. Tranf. N^ 472. p. 46 ; or vol. ix. p. 19. 

 of Hutton's Abridgment. 



This paper certainly difplays great ingenuity, and would 

 be of confiderable utility, provided the hypothcfis there 

 affumed were perfedly corred ; and even as it is, although 

 a different law may have place between the fpace through 

 which the fpring is drawn or compreffed, and its refiftance, 

 the fame principle of inveftigation muft ftill be preferred ; 

 and it may, therefore, be confidered as the foundation on 

 which the true theory muft be raifed, after a fufficient num- 

 ber of experiments has been made to affure us of the cor- 

 red law of their adion, not merely within the narrow limits 

 contemplated by the founder of the hypothefis, but through 

 all degrees of compreffion and extenfion, ftiort of that which 

 deftroys their original elafticity. We fhall therefore offer 

 no apology for exhibiting a concife view of the principal 

 theorems and dedudions of this ingenious author. 



Dr. Jurin commences his memoir with a few neceffary 

 definitions ; as the 



Length of a fpring, which is ufed to fignify the greateft 

 length to which a fpring can be forced inwards, or drawn 

 outwards, without prejudice to its elafticity. He obferves, 

 this would be the whole length, were the fpring confidered 

 as a mathematical line ; but in a material fpring, it is the 

 difference between the whole length, when the fpring is in 

 its natural fituation, or the fituation it will reft in when not 

 difturbed by any external force, and the length or fpace it 



takes 



1 



