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March 1, 1S6S. ] THE CIVIL ENGINEER AND ARCHITECT’S JOURNAL. 81 more the slate has been compressed, and the greater the weight of pressure to which it has been subjected, the longer will it last, and the finer is its cleavage. There is one description of stone which I do not think has been mentioned, and that is the Tottenhoe stone, a species of elunch, which is found in ^Bedfordshire, Herts and Bucks, of which so much has been used in the old churches from the end of the fifteenth century, but 1 think not previous to that. It seems they used better stones in earlier times, and with the decline of architecture, there was a corresponding decline in the selection of materials. I have myself seen that to be the case in Cornwall. There, in later times they used a great deal of granite, which was not used in the earlier periods ; but they have one stone found only in a single vein running through the south-east coast, of a most valuable kind. They call it the Pentuan stone. It appears about half-way up the cliffs, perhaps 150 feet high, and the bed seems to be about four feet thick. The mode of getting it is by men let down by ropes from above, and the blocks are thrown down on the beach within reach of the boats at low water, and thence loaded at half-tide. This stone was in great use in the fourteenth century and part of the thirteenth. I referred to the Tottenhoe clunch stone, because it has in every instance that I am acquainted with, gone to decay when used for outside work. But I have several times seen churches, where, after it had gone to decay, it had been plastered over to protect it from further decay ; but upon removing the cement, the stone was found to have gone several inches in depth beyond that, showing almost a more rapid process of decay, after being coated with cement than before. In a church in Suffolk, this stone was used consder- ably, and it has gone to decay very much in the same sort of w’ay. A stone mason in the locality told me, what he believed to be a remedy against this excessive decay, which 1 have never heard of elsewhere, and I think it would be valuable if its proves to be durable. I have tested it for three or four years with good success. How much longer it may last I do not know, but, from what I can judge of it as far as it has gone, I think it will add very considerably to the durability of this material. I say this, because some of the stones in the same building not treated in this way, have shown appearances of decay since that was done a year or two ago. The process to which I allude, is getting a number of lumps of lime in a bucket, and letting the water be boiled by the lime, without stirring up the lumps, and throwing the lime water on to the stone by a brush, taking care not to disturb the lime at the bottom; and that appears to form a fine crystalized infusion of lime. It seems to me that is a thing which would commonly answer the purpose with stone so absorbent. I suppose it is the absorbent nature of the stone, which enables it to take in that infusion better than a harder stone would. With regard to alum and soap, it may, I think, be a protection for a short time against the stone perishing, but I have myself tried it to keep out wet from brickwork, and it did not succeed. Mr. John P. Seddon, Hon Sec,—One of the points on which I am anxious to hear Professor Ansted’s opinion, is the class of stone most suitable for London. That raised with regard to slate is also an im portant question, and I for one should be glad to know what good green or grey slate may be relied on. I have myself used a grey slate from Delabole, in Cornwall, and was mainly instrumental in the opening of some quarries in Pembrokeshire, at Whitland, and near Haverford-west, having had my attention called to some slates upon old buildings in that part of the country, which were good in tone and colour, and which I was informed had been fifty years in use : these have since been intro duced into the London market, but my own experience has not been entirely satisfactory with regard to them. They are nice looking slates, but brittle, and some builders have expressed to me a doubt as to their durability, in consequence of which I have not used them lately. The green slate from the North Wales quarries seem to be of admirable quality, but there is so little of it to be got that it seems almost im practicable to obtain it; therefore if one could know whether the slates I have named or others are to be relied upon for durability, this dis cussion will result in great practical good. I have already sent some specimens of these slates to the Geological Museum, but the answer I had to my enquiries was, that it was difficult to give a definite opinion from specimens. With respect to the Cefn stone, which Mr. Ferrey mentioned as one which might be introduced into London, I, having used it at Aberystwith, should not be inclined to recommend it, for although I have used it as a walling stone, I found it less suitable and reliable for dressings. Bath stone is so very variable, that it is difficult to express a decided opinion upon it, but in my own practice, I generally come back to it, and I believe, if properly selected, and you can rely upon the builder you employ, it is about the best stone you can have. I have used it in exposed positions by the sea-side, where it has stood extremely well, and its moderate cost is of course a recommendation. I have also used the Ancaster stone at Great Yarmouth, giving a higher price for it in the hope that it would prove better than Bath. Shortly afterwards I was horrified at Cambridge, on seeing in buildings in pro gress there, this very stone, apparently in an advanced state of decay, before the walls were half up. I went back to my own building to see if anything of the kind was the case there, and though the stone had been far more carefully selected by the builder, yet I made up my mind that it would have been preferable if good Bath stone had been used instead. Dundry is a good oolitic stone, though its use has been discontinued for some time. For the works in the restoration of Llandaff Cathedral that stone was specified, and the quarries were re-opened to furnish the required supply, but as far as I could judge, though this stone is an excellent material, there is a considerable waste incurred from the great prevalence of sand holes it it. Whether better beds of it will be found I cannot say. One of the most valuable lime stones I have met with, is that known as the Camden; it is of a deep yellow colour and exceedingly good in quality, and if it would last in the atmosphere of London, I think there is no stone which would look better, the rich tone of it would be most desirable ; it is rather a hard stone, but it is not very expensive to work, and in that respect may be classed with the Ancaster and other of the hardest Baths. It is almost of the colour of yellow ochre. The Pennant sand-stone found through out Glamorganshire is exceedingly hard, and I believe it to be thoroughly reliable. Clunch, I apprehend, is a material which is only available for use in the immediate neighbourhood in which it is pro duced, it being of the nature of indurated chalk, being in fact the bottom beds of the chalk. If used with care, I believe it is very reliable, at any rate for interior work, but if it is used at all green in the winter time, it is liable to be blown to pieces by the frost. I have seen it used in buildings where th© carving was as new as when it was first executed. In St. Alban’s Abbey many of the tombs are of this clunch, and the carvings on them remain perfectly sharp. I may also just mention the white lias, which is found in Warwickshire, as being an excellent stone for carving, by reason of its close and fine texture, and suitable colour. Mr. Edwin Nash, Fellow.—I do not rise in the hope of being able to throw any light upon this lithological subject, for it is more lithological and mineralogical, than it is geological, and Professor Ansted has treated it in his paper as lithologically as it can well be managed. But I am induced to do so because no one has taken up the point which I brought forward at the previous meeting with regard to fire-stones. The learned Professor has told us that the carboniferous sand stones are the best for the purpose, and I took occasion to mention the blue Pennant stone, which is one of the carboniferous series ; it is too expensive for general use, yet, it is a most admirable material, and very suitable for tombs, for which I havo used it with the greatest satisfaction. Since the meet ing, I have tried a few experiments upon stones by putting them into a fire and plunging them in a heated state into cold water. The Rcigate fire-stone readily effervesces on the application of muriatic acid, shewing the presence of lime; yet, lime is an ingredient which seems to be undesirable in a fire-stone. I put a piece of that stone into a fire for forty-eight hours, and subjected it to wet immediately after wards, and it remained perfect, thereby keeping up its character of being really a fire-stone I and I think that stone ought to be analyzed for us, so that if we can find other analogous to it in composition, and at the same time of large sizes suitable for stairs and landings, such as we so much want in London, and which after being heated by fire will not go to pieces when water is applied, we shall get over one of the difficulties of making fire-proof buildings in London; and I am glad that Professor Ansted gives some hope in that direction with respect to the carboniferous sand-stones. I tried the experiment of forty-eight hours heating upon a piece of Craiglieth, that stone having been named by Professor Ansted, and while it was red hot, cold water was applied and the stone remained as perfect as when put into the fire. It is a good and well-known stone, but expensive. It seems to me to be of great importance that out of this discussion we should realise some absolute facts, which will be useful to us practically, and I have no doubt there will be several, but let that be one, and if we can elicit a knowledge of stones that best resist ths effects of fire, it will be a valuable thing for us, the subject being important at the present moment because there is an act of parliament in contemplation, by which certain buildings are to be erected in a fire-proof manner, and in which stone is to be forbidden. That sounds somewhat strange, but so it is; and if we can find a stone that -will not fall to pieces by the action of water at a fire, we shall have gained a grand point; and I am sure if Professor Ansted, with his thoroughly accurate knowledge (for that is the character of his information), will give us assistance in this respect, we may fully rely upon all that he tells us. Mr. E. W. Tarn, Associate.—There are a great many sand-stones which are but little known in London ; I refer to those of Yorkshire and Lancashire, with several of which 1 am acquainted. The York shire stone most known in London is that used as flags, landings and sills; but there are in addition to these, some of the finest building stones in England to be found in that county. In proof of this state ment, I may refer to the town halls of Leeds and Halifax, which are entirely built of Yorkshire stone. As far as my own experience goes, I find that the open grained stone stands the external atmosphere better than the elose-graiened and stones; and for staircases I do not think you can have any better material for fire proofing than the Yorkshire stones. As I have already said, they are little known in London, which perhaps arises from the fact of the Report of the Commissioners having entered very little into that matter. Thirty years ago, the facilities for railway transit were far less than they are at the present time, but Yorkshire is now so intersected with railways,
