1J5 



CONCRETE. 



CONDENSER. 



126 



a quality conceived generally and separately, without reference to any 

 object to which it belongs, as learning, length, wisdom, roundness. 

 Thus the names of classes are abstract, and the names of individuals 

 concrete ; and from concrete adjectives are made abstract substantives. 

 Concrete numbers are subject to the same explanation, being such as 

 indicate or directly imply a subject, as two men, five shillings, in con- 

 tradistinction to abstract numbers, which denote a conception of the 

 aggregate of two or five units. Concrete terms, in the scholastic 

 phraseology, are called paronyma. The following remark is from 

 Locke's ' Essay' (b. 3, c. 8, 1) : " This distinction of names shows us the 

 difference of our ideas ; for if we observe them, we shall find that our 

 simple ideas have all abstract as well as concrete names, the one a 

 substantive, the other an adjective, as whiteness, white, sweetness, 

 sweet." 



CONCRETE, an artificial conglomerate used by builders, princi- 

 pally in foundation works, when the subsoil is of a damp, or of a com- 

 pressible nature ; it is usually made of lime, sand, and gravel or broken 

 stone, and its useful action in the cases above cited consists in the 

 perfection with which this conglomerate forms a solid, homogeneous 

 mass a species of monolith, in fact, able to distribute the super- 

 incumbent weight over the whole surface it covers. Sometimes con- 

 crete is used as a backing to quay or retaining walls, and then its 

 successful application depends on the degree of hardness or solidity it 

 may attain, and to its powers of resistance to the transmission of 

 water. Occasionally, also, concrete is used as a walling material by 

 ramming it into moulds, which have, as matrices, the forms the 

 concrete itself is intended subsequently to represent in relief. Accord- 

 ing to the purposes the material is thus required to fulfil, it is neces- 

 sary to adopt more or less care and skill in its fabrication ; and indeed, 

 in some cases, the differences in the style of manipulation adopted are 

 so great as almost to render necessary the introduction of the French 

 word beton, to express a mode of making concrete which is essentially 

 unlike the one usually adopted in the greater part of England. 



The habitual mode of making concrete adopted in the south-east of 

 England, is to mix the yroitndntone lime obtained from the calcination 

 of the chalk marl (a species of argillo-calcareous stone, in which the 

 silicate of alumina is present in proportions varying from 8 to 14 per 

 cent, in the best varieties) with icreened bailout, or shingle, in the pro- 

 portion of one of ground-lime to 7 or 9 of ballast, measured in bulk ; 

 and to perform the operation of slaking, or of supplying the quantity 

 of water required for the subsequent crystallisation of the lime, simul- 

 taneously with the intermixture of the above ingredients. The lime 

 and ballast are then, after being frequently turned over, thrown into 

 the place they are intended to occupy, and in well-executed works they 

 are rammed carefully into all the corners of the foundations. In those 

 parts of England where the more decidedly argillaceous limestones are 

 used for the purpose of obtaining lime, greater precautions are how- 

 ever used, and are required ; for that class of materials absorbs water 

 under such very different conditions from the gray-stone lime, that the 

 slaking would not take place satisfactorily, if a longer time and a 

 more intimate contact between the lime and the water, than is admis- 

 sible in the case of the stone lime, were not allowed in the cases of the 

 use of the blue lias, or of the other limes possessing similar properties 

 to it. The precise nature of these properties will be discussed under 

 LrxE ; but it in advisable here to state, that the philosophy of the 

 action of that material is, simply, that it should form a binding or 

 cementitious substance, which should in its turn form the ganyue of 

 the other materials it is intended to connect. This is effected by pre- 

 senting to the caustic lime (deprived of its water of crystallisation and 

 of its natural dose of carbonic acid by calcination) the quantity of water 

 requisite to enable it again to resume a solid form around any given 

 object ; but it is found that the purer varieties of lime do not solidify 

 with sufficient rapidity, or in a sufficiently permanent manner, to allow 

 of their being used in building operations ; whilst the varieties which 

 contain certain proportions of clay (silicate of alumina) yield limes which 

 are able to set with rapidity, and even to resist the action of water 

 after a short time. It is on account of this power of resisting the 

 action of water, that some limes are called hydraulie, and the others 

 which do not possess it are called rum-hydraulic ; but the hydraulic 

 limes also have these characteristic differences from the non-hydraulic 

 ones, namely, that they absorb the dose of water requisite for their 

 crystallisation very slowly ; that they do not sensibly evolve much heat 

 in fixing the water ; and that they do not increase much in volume : 

 whereas the non-hydraulic limes absorb water rapidly, and begin at 

 once to decrepitate with a marked increase of volume, and a copious 

 evolution of heat and vapour. 



. the differences to be observed in the modes of making concrete 

 depend i >n these respective properties of limes. When the moderately 

 hydraulic limes are used, the operation of slaking takes place so 

 rapidly, that it may often be desirable to hurry the operations con- 

 nected with its mixture with the materials it is intended to unite ; 

 and at any rate there seems to be little danger of a subsequent 

 xlaking, when ground stone lime is used, and a fair quantity of water 

 is at once presented to it. But in the use of hydraulic limes, this 

 <i mode of treatment would be fatal to the successful result, for 

 with them it is essential that every particle of the lime should take up 

 it* dose of water, and that the whole of the mechanical changes in 

 the lime should be completed before the conglomerate itself is 



placed in its definitive position. It follows, therefore and herein 

 practice and theory agree that the more decidedly hydraulic a lime is, 

 the more perfectly must the operation of hydration be performed ; and 

 consequently, iu all cases where the hydraulic limes are used, it is 

 customary to mix them with the quantity of sand which would be used 

 to make ordinary mortar, under edge-rollers, and then to mix the 

 mortar so prepared with the screened ballast. This process is, in fact, 

 neither more nor less than the execution of rubble masonry with very 

 small materials; and the resulting material is the one to which it 

 appears to be desirable to apply the term faton, by way of contra- 

 distinction to the more imperfect and less valuable substance called 

 ordinarily concrete. The proportions of lime, sand, and ballast to be 

 used in the formation of beton must depend on the quality of the 

 lime ; it being always understood, that the more hydraulic a lime is 

 the less sand will it carry, but that, at the eatne time, this very same 

 quality renders its use more advisable for foundations to be executed 

 in water, or in damp situations. 



A very objectionable practice is sometimes adopted by 'he London 

 builders, when they use concrete in damp situations, of mixing ground 

 stone lime and ballast without slaking the lime at all, and of leaving 

 it to absorb the requisite quantity of water from the ground, or other 

 position in which the concrete is to be placed. Now, in such cases the 

 slaking must take place irregularly and unequally, and the changes of 

 volume thus produced must tend to disintegrate the mass. In fact, 

 whatever be the description of lime used, it is essential that the hydra- 

 tion should be completed before the concrete or beton is put in place. 



CONCUBINAGE is the cohabitation of a man with a woman, to 

 whom he is not united by marriage. Among the Romans, concubinage 

 was in use before the time of the Emperor Augustus, yet without 

 being formally permitted by law. Augustus, with the view of pre- 

 venting celibacy and encouraging marriage, A.D. 10, caused the famous 

 law called Lex Julia and Papia Poppsea to be passed, which may be 

 considered as much an ordinance of moral police as a- measure in 

 favour of population. This law contained several conditions advan- 

 tageous for those who had the greatest number of children. By the 

 same law, concubinage was legally allowed to unmarried men, with the 

 restriction that not more than one concubine could be taken, and she 

 must be a woman with whom marriage was not permitted, as women 

 of mean descent, freedwomen, &c. The concubine did not enjoy the 

 same rights as a wife, and the children begotten in concubinage were 

 not considered as legitimate, but were called natural (naturales), a 

 distinction which was of importance as to the right of succession. 



Concubinage being inconsistent with the principles of Christianity, 

 the Emperor Constantino the Great enacted laws against the institu- 

 tion, and it is now in all Christian countries considered unlawful. Yet 

 in Germany, among the reigning families, a left-handed or morganatic 

 marriage (Trauung an die linke hand or morganatische ehe) still 

 sometimes occurs. This kind of marriage resembles the Roman 

 concubinage, as well in its conditions as its consequences. 



CONCUSSION OF THE BRAIN, SPINE, fee. [HEAD, INJURIES 



OF THE.] 



CONDENSATION. [EXPANSION.] 



CONDENSER is the name given to any piece of apparatus used for 



cooling heated vapours, with a view of causing them to assume a liquid 

 condition. 



In the ordinary process of distillation, the condenser most commonly 

 d i.-, the warm-tub. Thia consists of a metal pipe usually 



