1844.] 



THE CIVIL ENGINEFilR AND ARCHITECT'S JOURNAL 



59 



llie surface. It is therefore, not tlie fault of limi'Stonc that wet iionctrates 

 bviildings, and it is frequently incurring unnecessary expense to avoid it on 

 tliat account, fur in most cases it is the fault of the mortar joints and not of 

 the stone ; and tliose portions of a Ijuilding erected witli tlie ordinary cut stone 

 of the present day, are frequently likely to be the least dry part of the struc- 

 ture, owing to the generally imperfect mortar joints. The absorbent stones, 

 such as the ordinary clay slates, and common earthy sandstones, are not 

 likely to resist the severe weather in exposed aspects without some external 

 protection. 



The second series of experiments relate to the sirenglli of the different kinds 

 of stone employed to bear superincumbent weights, or applied in various ways, 

 in which their resistance to I'racture is the point to be considered. [Mr. Wil- 

 kinson here exhibited a diagram, which showed in a familiar way the results 

 of the experiments. Slabs of the diflerent classes of stones were represented 

 of equal size and length, and a height ot wall shown resUng on tbem, varying 

 wuh the bearing power of the dilferent stones, the average, extreme, and least, 

 bearing of all be'ing given. The very great dill'erence at once showed the im- 

 portance which belonged to expL'riments of this kind, and how failures, which 

 frequently rciult from their improper use, might he avoided, and how far their 

 strength might be depended on, m applying them in any way diHerent from 

 that which they have been commonly and locilly applied.] Mr. W. contin- 

 tinued — I may here remark that the experiments have been very carefully 

 made, and the test has been applied by a powerful but well-adjusted lever, the 

 arrangement of our talented and scientific member. Mr. Mallei, by whose 

 kindness 1 have been allowed to use it. The result of the average of many 

 experiments is shown in the diagram, and the lines above and below represent 

 the extreme weak stones, and the extreme strong stones of each class. From 

 this it will bo seen that the strongest stones in resisting fracture are the slate 

 rocks. Some of these are stronger when the pressure is applied on the edges 

 of the laminae of cleavage than when applied on the faces.. The basalts are 

 next in strength, then the limestone, the granite, and the sandstones. Fortu- 

 nately for construction, that stone which is the strongest is that which sup- 

 plies the materials in the most useful forms for those portions of a building 

 in whuh such strenglli is required. I liave no doubt that the Valentia slate 

 rock will ultimately come into very much more general use, and that the 

 quarry will be of a considerable value ; stones can he raised from it neirly 

 30 It. long. 4 ft. or 5 ft. wide, and from 6 in. t5 12 in. thick, and it is probable 

 the use oi this material will elU'Ct a considerable change in many parts of the 

 interior constructive arrangement of buildings. .Such are the cotivenient sizes 

 and strength of the stone that it wouhl without any intermediate bearings or 

 support make the floor or ceiling of the room in which the Society is at pre- 

 sent assembled, the ends merely resting on the side walls, It can also be 

 easily wrought. The sandstones are the least satisfactory, and require great 

 caution in using them in any important constructive arrangement. The only 

 instance, among several hundred stoni! staircases, in which I liave encountered 

 any lailure Iroin the fracture ot the stones has been at Lisburn. where several 

 of the stone slops fractured cluse to the wall ; being a geomelrial staircase 

 the failure of one liroko the others. Now, in looking to the results of the 

 experiments wo find a satisfactory expUanation, because the stone here used is 

 till weikestof the whole; and though ihe stone quarries at Scrabo contain 

 some really good and useful material, the quality of it varies so much, as to 

 make it necessary to exercise great caution in its use. By recording failures 

 of this kind, however, much future inconvenience would be avoided. 



■fhe third series ot experiments was to ascertain the pressure required to 

 crush cubes of one inch sides. The second diagram represented by the differ- 

 ence in the heights of the walling over columns of the same size, but supposed 

 to be ot the different kinds of stone, their relative strength, the columns being 

 considered as the stones on which the pressure was exerted. The order of 

 strength in this case differs from that ascertained in the experiments on frac- 

 ture, as shown in the first diagram. When subjected to crushing, the basalts 

 proved the strongest, the limestones, .and successively the slales and sanil- 

 stoiies; the quality of the latter is exceeding variable, and show the great ad- 

 vantages to be derived from recorded. facts. Of the diflerent varieties of the 

 limestones, some of ihe largely crystalline stones, and the compact hard calp, 

 are the strongest. The light coloure J crystalline stones of Ardbraccan, and those 

 around Cork, are among the weakest. The Connemara while marble, or pri- 

 mary limestone, is Ihe strongest of all the limestones I have yet met with. 

 Among the strongest sandstones are the red rocks of the soulli, and the hard 

 qiiarlzy grits of ihe north-west of Ireland. Among the weakest are those of 

 the county Down quarries, and the sandstones in Antrim and around Clonmel, 

 and some of the coarse quartose sandstones of Donegal. Of the slates, those 

 from Valentin, as proved by several experiments, resist less pressure than 

 those of Killaloe, and those from Mr. .Synge"s quarries in Wicklow are about 

 intermediate. Of ihe granites 1 have given nocompantive results, not having 

 yet completed sufficient experimenls to enable satisfactory conclusions lo be 

 drawn. I miiy mention, however, that, from several trials, the results do not 

 give granite any superiority over many of the stones in ordinary use. 



From the foregoing experiments, which I apprehend to be sufficiently nu- 

 merous to allow of some general jiraclical conclusions, itis clear that relation 



generally exist between the weight and degree of absorption of stone?, the 

 lightest being the most absorbent, and the heaviest the least so ; but this rela- 

 tion is not const.intly uniform, .and in some varies considerably, -is might rea- 

 sonably be expected. Nor is it prob,ablo that, however carefully the stoni'S 

 might be weighed, either under an exhausted receiver of an .air pump, or in 

 any other way, that any results would be obtained. dilTering much from the 

 conclusion here arrived at. Nor is there any uniform relation between the 

 same kind of stones when used in diflerent ways ; for, used as a column, or in 

 any other position where a weight would be exerted to crush if, the basalts, as 

 shown by the foregoing experiments, may exceed all others, and yet occupy 

 an inferior position in the scale when applied to support a weight over an 

 opening, or as an architrave resting on columns (the peculiarity of mineral 

 char.acter rendering one stone better for one purpose than anotlier) as the 

 particles of the stone are uiflerently acted on; and although this may 

 be at variance with a commonly received opinion, I have full con- 

 fidence in the general result of the present experiments which are very de- 

 cided, and 1 believe much more numerous than any others of the kind which 

 h,ave been made. And however close the relation may be, wdiieh would ap- 

 pear from othor experimenls to exist between the crushing and fracturing 

 strength of similar bodies, it is very clear to my mind Ihat this law does not 

 extend to stones, which, as aggregated or compound bodies, may be expected 

 to diflijr much in exjierimcnfal results from those which are sim|>le. In con- 

 clusion, I trust that these'experiments will be received by the Society as inci- 

 pient attempts to establish some positive data in this neglected but important 

 branch of their study, and hope that they may be the same moans of in- 

 ducing others, better qualified, to pursue the subject. 



NOTES OF THE WEEK. 



It was with great regret we learned that the Council of the School of 

 Design had succumbed to the clamours of interested parties, and given up 

 the class of wood engraving for females. The strong remonstrances of the 

 press have, however, procured its restoration. The necessity of providing 

 suitable employment for females would alone entitle any proposition for ef- 

 fecting this to favourable attention, from motives of common humanity. 

 Then, too, it should be considered, that it is perfectly legitimate to give ele- 

 mentary instruction in any branch of the fine arts. We never heard of 

 sculptors inveighing against the Royal Academy, or architects against any of 

 the numerous public institutions for giving instruction in their art. The 

 elementary processes may indeed be taught, but genius and refined taste 

 cannot so well be communicated. Just imagine Landseer, Maclise and 

 Westmacott applying to the Government for the prohibition of all public 

 schools of art, what a lamentable spectacle would it present. If the School 

 of Design can invent any process for making young girls first-rate engravers, 

 ■we say so much the better, let them do it; hut if, as we believe, they cannot 

 communicate inspiration, but only create mechanical skill, we say again so 

 much the better, for it will tend to reduce the price of inferior works, which 

 now have to be paid for at high rates without any adequate cause. The 

 remuneration of first-rate talent instead of being reduced by this measure is 

 much more likely to be increased, while much good will be done by reducing 

 the price of merely mechanical performances, and providing suitable employ- 

 ment for many females. It is ridiculous to assert that a common diagram 

 engraved on wood is a work of art, and is to be paid for as an artistic pro- 

 duction. 



The Society of Arts has had a legacy left to it of £.5000, and University 

 College receives £14,000 under Mr. Brundrith's legacy. 



We were amused to learn that a Theatre Royal has been erected in New 

 Zealand, which altliough of slight materials, is illuminated with gas. 



A fine statue of the Qneeu has been erected on the top of the grand 

 portico of the Royal Institution at Edinburgh. It is from the chisel of Mr. 

 Steele, and has attracted much admiration. The height of the jiedestal and 

 statue is ISfi., and the Queen is represented with a diadem, and in her robes 

 of state, holding the orb in her right hand, and in a sitting posture. It is 

 esteemed a very fine ornament to Edinburgh. 



The Sth and 9th of April are the days named for sending in works of art 

 to the Royal Academy for the ensuing exhibition. 



M. Jacques, a French sculptor in Russia, has met with a great misfortune 

 in the destruction by fire of his model for a colossal statue of the Neva, 

 by which the labours of four years were lost. 



Signer Lanzaru?lo of Rome, has, it is said, discovered the means of fixing 

 on lithographic stone, daguerreotype impressions. He has presented to the ' 

 Pope several plates of the public buildings of Rome. 



It is said, that .Mr. Clegg is going to Berlin for the purpose of laying down 

 an atmospheric railway from Berlin to Charlottenburg. 



The monument raised by pulilic subscription to the Prince of Condi', in 

 France is finished. It is by M. Fauginet, sculptor, and M. Leveil, architect, 

 and consists of a column and a cross of marble, 40ft. high. The base is 

 decorated with statuary. 



Overbeck is at Rome at work on a jiicture for one of the churches of Lu- 

 beck, his native place, and for which he is to receive 1000 ducats. 



