14 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Jan. 13, 



in Mliicli It can he applied llie liellcr, ami, as bone linst is a line snlislancc il 

 is (iftcn useil willi ailvimlage. When Ijonc was (irst empUiyed, it was inia- 

 gincJ that it was only tlie animal part tliat was wnrtli anything ; the l.ones 

 Aieie therefore broken up. anil as long as they eniillcd a disagreeable cffliiviiim 

 it was thought they were doing their duty. It was aftenvards found that 

 the earthy iiortion also did its part, which is hy no means an unimportant 



one. 



Phosphate of lime, instead of being applied as ground bone, should be dis- 

 solved and mixed with sulphuric acid, when it may he applied with consider- 

 able advantage. It may, perhaps, be .said, that the acid might be fatal to the 

 crop, but this is not the case, the soil, in all probability, contains lime, and 

 the sulphuric acid acting on this, produces sniphale of lime, and you would 

 thus procuie sulphate of lime, and phosphate of lime, both of which are valu- 

 able substances. Some notion of the immense ([uantity of phosphate of lime 

 contained in certain vegetables, may be gained by referring to the (juantity 

 contained in the bones of animals. In the intestines of horses, especially, we 

 occasionally find large masses of phosphate of lime derived from the hay and 

 oats whicli they consume. 



I must now pass on to what should have been the exclusive subject of our 

 meeting this evening, namely, the consideration of clays. This is a very im- 

 jiortant subject, but one which we can only attend to, on the present occasion, 

 as regards the leading points connected with them. In the first place, we 

 know that a great part of the surface of all countries consists of w hat is called 

 clay. We .also know that very different substances pass under this name ; 

 .all, however, agree in containing one element which is peculiar to clays. 

 This element used to be called argil or argillaceous earth, but it has lately 

 been called alumina because one of the elements of alum. To obtain it you 

 may take a common solution of alum, and then add an alkali, which will 

 decompose the alum and produce a wliitc flocculent prccipilale, which is alu- 

 mina. It is this which gives to clay its elasticity, and itsrclentiveiiess wiih 

 regard to water. It is a substance which has a strong affinity for water, 

 and if, therefore, wc take the pains to collect this precipitate, and dry it, 

 we shall find that it lakes up a considerable quantity of water. This is 

 one important property belonging to this part of clay. 



Another important properly is, that it has a strong affinity tor vegetable 

 matter; and now, when «c talk of fixing elements in agriculture, we may 

 say that aluminous earth fi.\es organic matter. Here is an e,Ni)eriment. You 

 see a quantity of clear water with a brown precipitate at the bottom : this is 

 merely an infusion of vegetable extract which has been mixed with .alumi- 

 nous earth. The aluminous earth has taken all the vegetable matter out of 

 tl'.c water. Thus 1 fix organic matter ; and if this would happen in the soil 

 it would be very useful, as it would keep tlie organic matter in that posilion 

 in which it would be most u.selul to the crops. 



There are some chemical peculiarities belonging to this substance by which 

 aluminous may be distinguished from other earths. If to the above preci- 

 pitale I add soda or pot.ass, or an acid, the precipitate will be re-dissolved ; 

 and I must tell you that alumina is soluble both in alkali and acid. .Mnmina 

 is on the whole a very extraordinary substance. 



Another component part of clay is silica. You are all acquainted with 

 this substance in its pure form, as a beautiful mineral, rock crystal ; it is 

 also known as common flint, and is sometimes beauiifully coloured, as in the 

 amethyst. There area great variety of rock crystals exhibiting themselves 

 in different form. Chalcedony is another form of silica which must have been 

 in solution ; and we may infer that silica has been dissolved in water and 

 has not been fused. Another form of silica is common sand, a substance 

 which we frequently do not reg.ird in all the important bearings which be- 

 long to it. IJut it is beautifully applied, as the boundary of the ocean, being 

 insoluble in water, and well adapted to resist the influx of the waves ; it is 

 the only substance indeed that would be applicalde to that purpose save hard 

 rocks, for we all know the effect of the ocean upon soft rocks and banks of 

 shingle. Besides being insoluble in water, sand cannot lie solved in any 

 common acids ; it can, indeed, only be solved in one acid, and that is a very 

 rare one. Now we see the dilTerence between silica and alumina, the latter 

 being soluble in all. 



If we fuse a mixture of silica, potass, and soda, we obtain glass ; if we 

 increase the qu intity of silica, we have glass not easily fusible; if we 

 increase the quantity of soda, we get glass very fusible, and ultimately we 

 may obtain it soluble in water. Now here I have that extraordinary .sub- 

 stance flint in a soluble state, and if 1 considerably dilute it I shall have 

 what the old chemists called " liquor of flints ;' and I find now, if I add 

 acid to it, that 1 can throw down the silica first in a gelatinous state ; then 

 if 1 use a stronger solution, I find that it w ill become as hard as flint. 



As you will find that silica constitutes an essential ingredient in grasses 

 and a great variety of plants, you can understand that it gels to them by 

 being brought into a soluble state, principally by the action of an alkali. 



With regard to the term clay, it is sometimes thought to be applied to 

 pure alumina, but this does not exist in a native state, except in the sapphire 

 and other magnificent gems, which are composed of it. Common clay con- 

 tains a greater quantity of .silica than alumina, yet it derives its leading 



properties from alumina. AVe find, for instance, that when a soil contains a 

 great quantity of alumina, it is known under the name of " strong clay " 

 or " stiff clay," and so on through the diflerent varieties of loam, sand.^, 

 Stc. ; as, for instance — 



When in 100 parts of soil there are 10 of clay, it is termed sandy. 

 When from 10 to 40, sandy loam. 

 40 to 70, loam. 

 ,. 70 to 85, clay loam. 

 „ 8.5 to i)5, strong clay. 

 ,, 05 to 100, agricultural clay. 



Clays also contain potass, soda, and sometimes phosphate of lime, and it 

 is in consequence of the soda and potass w liich they contain that tliey be- 

 come such important ingredients in the soil. We know how much the tex- 

 ture of the soil depends upon clays — that is mechaiiicil ; but their great 

 chemical properties ilepend upon their power of retaining water, and their 

 containing a certain quantity of potass and soda. 



If clay contains a large quantity of potass and soda it contains a great 

 agricultural tre .sure, and if we can get out these alkalis they become very 

 valuable. The question, therefore, occurs, " How are we fto ascertain if the 

 soil does contain much alkali ?" This is done easily by a common chemical 

 process, wdiich, however, I cannot go through here, because I cannot bring a 

 furnace before you. I will, however, make use of electricity, to show you 

 Ihat there is alkaline matter in this clay. And 1 do it so: — I take some of 

 this powdered clay — it contains some oxide of iron — and I place it upon this 

 plate of platina, 1 now moisten it with a drop of water ; and the question I 

 wish to determine is, whether there is alkali in this clay, which I have 

 washed so as to take all the soluble salts out of it ; now I will make this 

 part of the electric circuit — now I am decomposing it, and doing what I 

 might do in a furnace by means of lime and other agents— and now you 

 may see the dcNclopnient of alkali : here I should remark to you that elec- 

 tricity is a great chemical analyser, and resolves things into their elements 

 in a wonderful way. 



Amongst other peculiar properties belonging to clays, are the absorption 

 of air, ammonia and nitric acid. Strong clay is used for a variety of useful 

 purposes, and we have here a subject of great importance on whicli much 

 might be said — draining, in which the application of clay for tiles, Sic, is 

 most convenient. 



I have now concluded the task wdiich your Lordship did me the honour to 

 impose upon me. On all future occasions I shall be happy to assist ycnir 

 e.xcelleict society with any information which I may possess — and I need 

 hardly say that this is a branch of science in which much remains to be ef- 

 fected. 



At the conclusion of this and the preceding leclure. His Grace the Duke 

 of Richmond, K.G.. in a speech highly eulogistic of the abilities and kind- 

 ness of the learned lecturer, jiroposed a vote of thanks to Professor Brande 

 for the able and interesting address with which he had favoured the society. 

 Philip Pusey, Esq., M.P., oneach occasion seconded the votes, which were 

 carried with acclamation. 



THE TEMPLE OF MINERVA, OR THE PARTHENON, 

 ATHENS 



The fine arts attained their greatest perfection in Greece during the 

 period extending from the 80th to the lllth Olympiad, (/. e.) from 

 the year 460, to the year 336 before Christ, whicli comprises the age 

 of Pericles and Alexander; and to this period the most admirable 

 masterpieces now in existence must undoubtedly be referred. Poli- 

 tical events had long been preparing the way for this glorious advance. 

 The Persian war, by the agitation it produced throughout the whole of 

 Greece, bad given an impulse and activity to the mind of men, which 

 were the principal causes of this stupentlous progress. Athens had 

 been the grand theatre of the struggle, and consequently the operation 

 of these causes was felt there in all its force. The successful issue of 

 the war, by inflaming the nation, awakening it to a keen perception of 

 its greatness, and inspiring it with a noble patriotic pride, raised its 

 intellectual faculties still higher, and led to those astonishing improve- 

 ments in art, particularly in Attica, which, as we learn from Herodotus 

 (lib. V. cap. 78), began to appear in the fourth year of the t)7th 

 Olympiad. 



Athens had the honour of producing Cimon and Pericles, at an epoch 

 when its glory, power, and revenues, Iiadreached their utmost limit. 



' We are indebted to the conductors of the illustrated work on Ancient 

 and Modern Architecture, published by Messrs. Didot, for permission to 

 insert the above interesting paper. It will afford a favourable specimen of 

 the manner in which the work is got up, and will, we hope, justify the high 

 terms of approbation which we have felt it our duty to express in relation to 

 this valuable work. — Ed. C. E. & A. Jour. 



