lolf 



COFFIN. 



ox: wiir.r.i. 



protect the earthwork from the effect* of any current which may exist 

 in the stream; but when a double enclosure is resorted to, it is 

 frequently so strengthened by strut* and cross-bracing, that the whole 

 of the resistance to the water U obtained from them, whilst the earth 

 contained within the enclosure only performs the function of excluding 

 the passage of water from one side of the dain to the other. The 

 simple dams backed with earth are often used to protect tlx- founda- 

 tions of abutment-walla of bridges, of wharves, 4c., immediately con- 

 nected with the shore ; whilst the double enclosure U almost always 

 adopted when the foundations of piers, or other works in deep, MM 

 streams, require to be executed with particular care. It is to be 

 observed, also, that in the construction of coffer-dams the consideration 

 of the lateral displacement, by reason of the tendency to slip upon the 

 bed, is of less importance when timber enclosures are used, than it is 

 in ordinary earth-work dams, because the hold of the piles in the 

 ground enables them to resist that particular action; whereas the 

 earthen dams only resist by the friction upon the surface of their 



Assuming that in either case (that is to say, whether timber or 

 earth- work be used) there is no danger of lateral displacement of the 

 dam, the pressure which will be brought to bear upon the portion 

 exposed to the dynamical action of the water is thus calculated : 

 Taking d to represent the depth of water in feet lineal, the pressure 

 per foot lineal of the dam will be proportional to the weight of a right- 

 angled triangle of water, whose sides = d ; or as a cubic foot of water 



weighs 62} K*. nearly, the pressure will be x 624 i 



calling the 

 length of the dam, in feet, /, the total pressure will be = I x 125</ ' 



According to the laws of hydrodynamics, the centre of pressure is of 

 course situated at ^d from the bottom ; and therefore, if only one stay 

 be necessary, it should be placed at that point If more than one stay 

 be necessary, on account of the great height of the dam, the succeed- 

 ing ones must be placed at the centra of pressure of the other portions ; 

 or in other words, if three stays be employed, they must respectively 

 be fixed at points measuring , }|, and Jf from the bottom of the dam. 

 In ordinary cases the dam is, however, made of a rectangular section, 

 and does not depend on struts ; and when this form is adopted, the 

 thickness, or width, may be calculated as follows. Calling w the mean 

 weight of the dam per cubic foot, h its height in feet, and d the depth 



of water; then t, the thickness, should be, t = ' /125 d * ; for the mo- 



inent 



resistance of the dam is = 



f , and that of the water 



According to Mr. Neville (whose paper on this subject, 



in the ' Civil Engineers' and Architects' Journal,' 1849, contains the 

 best practical information on the subject yet printed), it is customary 

 to take the weight of a cubic foot of a coffer-dam at [90 Ibs., but to 

 reduce it to 30 Ibs. per foot, if the water should be able to get under 

 it* seat If struts should be used, Mr. Neville states that the distance 



of their feet, called I, should be made equal to - - _, following, 



Ghut 2 



however, the notation adopted above, and supposing t, the thickness of 

 the rectangular portion of the dam, to be given. This is usually the 

 case in practice ; for the hydroscopic qualities of the clay, used to fill 

 in the space between the timber casings of such dams, requires that 

 they should be at least from to 2 to 3 feet apart ; generally speaking 

 the distance between the outer and inner rows of piles is made 4 feet 



In the execution of coffer-dams, the system usually adopted is to 

 drive guide-filet to mark the general limits of the enclosure. Horizontal 

 ichalei, as they are called, are then attached to the guide-piles, and 

 they serve to keep in place the cUae or the sheet piling, which forms 

 the exposed face of the dam ; occasionally, when great perfection of 

 execution is required, the close piling is made with vertical grooves, or, 

 to use the workmen's phrase, it is grooved and tongued. The inter- 

 mediate space between the inner and the outer rows of sheet piling is 

 then filled in with impermeable clay puddle ; and when all connection 

 between the external and the internal waters is thus intercepted, the 

 Utter is pumped out, so as to allow the ordinary building operations to 

 be carried on as though on the dry land. 



Verv good descriptions of coffer-dams actually executed, under 

 difficult circumstances, are to be met with in Perronct's 'Num.!!. 

 Architecture Hydraulique ; ' in Sganzin's ' Cours do Construction ; ' 

 in Semple's ' Treatise on Building in Water; ' and in Cressy's ' Treatise 

 on Bridges and Vaults.' 



COFFIN, the box or chest in which dead bodies are put into the 

 ground ; also a mould of paste for a pie : from the Latin cvMniw, and 

 that from the Greek K<tyu>of, which properly meant a wicker basket 

 Wyntown , in his ' Chronicle,' uses cofyne for a shrine or box, anil i n 1 1 1 . 

 ' Pericles ' of Shakspere at least of his time it is so used : " Bid 



Nestor bring my casket and my jewels ; and bid Nicander bring 



me the satin coffin." We have another instance of the uw "ft 1 

 coffin for an ordinary chert in the Wardrobe Accounts of Edwin. I IV.. 

 8vo. Lond., 1830, p. 125 : " For closyng and fastcnyng of divers nfyni 

 t fyrre, wherein the kyng'n books were conveyed and caried from the 

 king's great wardrobe in London to Eltham, V 1 ." The kiittvaen, or 



"n composed of rough stones, set edgewise at the sides and ends, 



and covered with one or more 'flat stones, was common among the 

 Britons ; they are found in caverns, Ac. in various parts of the king- 

 dom. Sir Christopher Wren found stone coffins of the Saxon times, at 

 the rebuilding of St Paul's : and Gough adds that, from the 9th 

 century to the reign of Henry III., stone coffins were in general use, 

 that is, for persons of the higher classes. The bodies of the common 

 people, not only in the Norman but also in the English ten, as we see 

 in the illuminations of ancient missals, were only wrapped in 

 and so put into the ground. In this manner, Matthew Paris in 

 us, the monks of St. Alban's were buried, till the time of Abbot Warm, 

 who died in 1195. He ordered that they should be buried in 

 coffins, as more decent. Matthew Paris, on this occasion (' Vit, AM.. 

 S. Alb.,' p. 95), charges him with innovations on established customs, to 

 please the multitude. Many stone coffins remain of the 1 1th, 12th, and 

 13th centuries with crosses, crosiers, mitres, and inscriptions carved on 

 the lids. Strutt says, in the reigns of Henry V. and VI., stone coffins 

 wore made with necks, distinguishing the head and shoulders. Coffins 

 both of lead and wood are of early use. The former occur in numerous 

 instances through different centuries : and that the Saxons buried in 

 coffins of wood, occasionally, we have the testimony of Bede. Ceadda 

 was so buried (' Hist. Eccl.,' 1. iv., c. 3), as was Etheldreda, wife of 

 Egfrid, king of the East Angles. (Ibid., 1. iv., c. 29.) Sebba, king of 

 the East Saxons, was buried at St. Paul's in a coffin of gray marble. 

 (Ibid., 1. iv., c. 11.) The forms and ornaments of various ancient 

 coffins, mostly of stone, may be seen in the plates of illuminations in 

 Strutt's ' Manners and Customs,' vol. i., pi. xxxix., xlv., lxvi r and in 

 Cough's ' Sepulchral Monuments.' 



COGNO'VIT, or more technically cognovit actloiiem, is a formal 

 acknowledgment or admission by one person, commonly a defendant, 

 that another person, ordinarily the plaintiff in an action, has a good 

 right of action or just claim against him. Thus it is not unusual for 

 a defendant, when served with a writ for a claim to wlu'ch he has no 

 answer, to give a warrant of attorney as it is called ; that is, in effect, 

 to admit the plaintiff's claim, so that all expense is saved, and judg- 

 ment at once entered up for the plaintiff. In almost all cases the 

 defendant's failure to appear to a writ is, in effect, a cognovit actionem, as 

 the plaintiff may, if the action be for the recovery of a specific amount, 

 at once sign judgment for that amount. If the action be for damages, 

 he may sign an interlocutory judgment by default after certain forms, 

 and afterwards ascertain the amount for which he is entitled to .lintU 

 judgment by the verdict of a jury. The advantage of having a claim 

 admitted beyond dispute has made it a common practice for a debtor 

 to strengthen the security of hia creditor by executing a warrant of 

 attorney to an attorney named by the creditor, authorising him to 

 confess a judgment in an action to be brought by the creditor against 

 the debtor for the specific sum due to him. In order to prevent 

 debtors being defrauded, such a warrant of attorney or cognovit is of 

 no force unless there be present an attorney of one of the superior 

 courts, on behalf of the party who gives it, expressly named by him, 

 and attending at his request, to inform him of the effect of the instru- 

 ment before he executes it, and who must subscribe as a witness to 

 the execution, and declare himself to be the attorney for the party. 

 In order to be effectual as against the assignees of the debtor, if he 

 should become bankrupt or insolvent, warrants of attorney and cog- 

 novits must further be filed in the Court of Queen's Bench within 

 twenty-one days after execution. 



(1 & 2 Viet. c. 110. Chitty's Practice, by Prentice, tit. 'Cognovit' 

 and ' Warrant of Attorney.') 



COG-WI1KKU The tooth-wheels used in machinery for the trans- 

 mission of motion are called ruu-ieluil* when the teeth ore made of 

 wood ; when the teeth ore of iron such wheels are simply called iwth- 

 wJteeli, and subsidiarily they are known as pinions, bevilled wheels, 

 annular, or crown wheels, according to their sizes and their relative 

 positions with respect to the rest of the machinery. [MACHINEUY.] 

 Both cogs and teeth, however, are the projections on one wheel fitting 

 into the space left between the two teeth of the corresponding wheel, 

 in such wise that one of those wheels cannot move without putting 

 the other in motion. The thictnesi of cogs, or teeth, is measured on 

 the jiitch circle of the wheel ; and the interval between one cog ami t If 

 next to it is called the depth, and is made equal to the thickness, 

 augmented by from fa to ^ of that dimension, according to the per- 

 fection of the work. The breadth of a cog is its dimension upon the 

 axis of rotation ; the portion of its height (or of the clear united length 

 from the top to the bottom of the cog) which lies beyond the pitch 

 circle is called the face; and that which lies within that circle is called 

 the Jhnk. The jiitch of wheels of this description in the distance 

 measured from centre to centre of the cogs, or of the intermediate 



. . 



Cog-wheels are usually made with cast-iron frames, in which rectan- 

 gular holes are left to receive the wooden cogs or teeth, and these pass 

 through the whole thickness of the rim, and are retained in their 

 situations by means of keys or wedges. The cogs are thus wedged up 

 iieing cut into their definite form, and the latter must be set 

 out with all the care usually observed in executing teeth-wheels. 

 [TooTH-wni 1 1 | \\lnii well made, cog-wheels are preferable to ordi- 

 nary teeth-wheels, especially in large work, on account of their working 

 more smoothly and with le noise; but great precautions must be 

 observed in the selection of the wood of which the cogs are made, and 



