CIVIL ARCHITECTURE. 



595 



Deca 



by a certain mixture of pitch and tar, upon which they 

 strew small pieces of cockle and other shells, beaten al- 

 most to powder, and mingled with sea-sand, or the scales 

 of iron, beaten small and sifted, which incrusts, and 

 it, after an incredible manner, against all these as- 

 faults and foreign invaders ; but if this should be deem- 

 ed more obnoxious to firing, I have heard that a wash 

 made of alum has wonderfully protected it against the 

 assault even of that devouring element ; and that so a 

 wooden tower or fort at the Pirzum, the port of Athens, 

 wa defended by Archelaus, a commander of Mithridates, 

 against the great Sylla. But yon have several composi- 

 tions for this purpose, in that incomparable Treatise of 

 Naval architecture, written in Low Dutch by N. Wit- 

 sen, Part I. chap. vi. The book ia in folio, and he that 

 shou'd well translate it into our language (which I much 

 wonder has not yet been done) would deserve well of 

 the public. 



" Timber that you have occasion to lay in mortar, or 

 which is in any part contiguous to lime, as doors, win- 

 dow-cases, groundsels, and the extremities of beams, &c. 

 have sometimes been capped with molten pitch, as a mar- 

 vellous preserver of it from the burning and destructive 

 effects of the lime ; but it has since been found rather to 

 heat and decay them, by hindering the transudation 

 which those parts require ; better supplied with loam, 

 or strewings of brick-dust, or pieces of boards ; some 

 leave a small hole for the air. But though lime be so 

 destructive whilst timber lies thus dry, it seems they 

 mingle it with hair, to keep the worm out of ships, 

 which they sheath for southern voyages, though it is 

 held much to retard their course. Wherefore, the Por- 

 tuguese corch them with fire, which often proves very 

 dangerout ; and, indeed, their timber being harder, is 

 not so easily penetrable. 



" For all uses, that timber is esteemed the best, which 

 is the most ponderous, and which, lying long, makes 

 deepest impression in the earth, or in the water, being 

 floated ; also, what is without knots, yet firm, and free 

 from sap, which is that fatty, waiter, and softer part, 

 called by the ancients alburnum, which you arc diligent- 

 ly to hew away. 



" My Lord Bacon, Exper. 658, recommends for trial, 

 of a found or knotty piece of timber, to cause one to 

 speak at one of the extr -mes to his companion, listening 

 at the other ; for if it be knotty, the sound, says he, wifi 

 come abrupt. 



" For the place of growth, that timber is esteemed 

 best which grows most in the sun, and on a dry and hale 

 ground ; ftr those trees which suck and drink little are 

 most hard, robust, and longer lived instances of so- 

 brifty. The climate contributes much to its quality ; 

 and the- northern situation is preferred to the rtst of the 

 quarters ; so as that which grew in Tuscany was of old 

 thought better than that of the Venetian side ; and yet 

 the Biscay tin.ber is esteemed better than what they have 

 from colder countries ; and trees of the wilder kind and 

 barren, than the over much cultivated and great bear- 

 ers." 



Dr Parry liai published an excellent paper on the cau- 

 ses of the decay of wood, and the means of preventing 

 it. From it we take the liberty of abridging what foH 

 lows ; but would recommend a careful perusal of the 

 whole of it to those who wih for further information on 

 the subject. * 



Wood Dr Parry supposes to be subject to destruction 

 from two causes, rotting and the depredations of insects. 



Of rot there are two supposed kinds, the first takes ^Practice 

 place in the open air ; the second under cover. S "Y""" 



When perfectly dry, and in a certain degree of tem- 

 perature, both animal ind vegetable matters seems scarce, 

 ly capable of spontaneous decay. On this principle, fish 

 and other animal matter ij often preserved. 



" Similar causes produce the same effects on wood. 

 Even under less rigid circumstances of this kind, as in 

 the roofs and other timber of large buildings, it conti- 

 nues for an astonishing length of time unchanged. Wit- 

 ness the timber of that noble edifice, Westminster-hall, 

 built by Richard II. in 1397 ; and the more extraordi- 

 nary instance quoted by Dr Darwin, in his ingenious 

 work the Phytologia, of the gates of the old St Peter's 

 church in Rome, which were said to have continued 

 without rotting, from the time of the Emperor Constan- 

 tine to that of Pope Eugene IV. a period of eleven hun- 

 dred years. On the other band, wood will remain for 

 ages, with little change, when continually immersed in 

 water, or even when deeply buried in the earth, at in 

 the piles and buttresses of bridges, and in various mo- 

 rasses. These latter facts seem to show, that if the ac- 

 cess of atmospherical air is not necessary to the decay 

 of wood, it is at least highly conducive to it." 



Putrefaction is the cau of rotting, and putrefaction p utre f ac . 

 is occasioned by stagnant air and moisture. The moisture tjou. 

 of the air, coming in contact with wood of a lower tempe- 

 rature, is condensed in the same manner, as is more visi- 

 ble in our glass windows. In order to prevent the bad 

 effects of this condensation, currents of dry air ought to 

 be made to pass in contact with the timber. Of the ad- 

 vantage* of this, the Gothic architects seemed aware ; 

 for it wa common with them to leave openings for this 

 purpose a practice which we could strongly recommend 

 in cellars, &c. 



" It appears that the contact of water and air are the 

 chief causes of the decay of wood. If, therefore, any 

 means can be devised, by which the access of moisture 

 and air can be prevented, the wood is eo far secure 

 against decay. This principle may be illustrated, by 

 supposing a cylinder of dry wood to be placed in a glass 

 tube or case which it exactly fills, and the two ends of 

 which are, as it is called, hermetically sealed, that is, 

 entirely closed, by uniting the melted sides of each end 

 of the tub. Who will doubt that such a piece of wood 

 might remain in the open air a thousand years unchan- 

 ged ? Or let us take a little more apposite illustration 

 of this fact, that of amber, a native bitumen or resin, 

 in which a variety of small flies, filaments of vegetabks, 

 and others of the most fragile substances, are seen im- 

 bedded, having been preserved from decay much longer 

 probably than a thousand years, and with no apparent 

 tendency to change for ten times that period." 



These observations lead to the theory of painting 

 timber, for the purpose of preserving it. 



Mr Bat-on of Limehouse is of opinion, that the dry Dry ret. 

 rot proceeds from a plant, called Boletus Lacryman*, one 

 of the fungus tribe, and is one of the few that have 

 leaves as the misletoe. But Dr Parry justly observes, 

 that these plants " begin merely, because decayed mood 

 is (heir proper soil." 



" The smell which we perceive in going into vaults or 

 cellars, where this process is going on, arises partly from 

 the extrication of certain gases, mingled perhaps with 

 some volatile oil, and partly from the effluvia of those 

 vegetable substances, which have already been said to 

 grow on it, ar.d which, though they beirin merely because 



Paper* of Bath and West of England Society, voL xi. p. 2J6. ; also Nicholson's Journal, No. 85, 86, and 87 



