98 ,/lrchiteclure.

then will the necessity-, as well as the propriety, of having a distinctive character for cemeteries be understood and appreciated.

The planting of" ./lowers in cemeteries is very general, not only in the margin of masses and belts, and in beds, as in pleasure-grounds, but on graves. For our own particular taste~ we would have no flowers at all, nor a n y p o r t i o n of ground within a cemetelv~'" that had tile appearance of being dug or otherwise moved for the purpose of cultivation. A state o f quiet and repose is an important ingredient in the passive sublime ; and moving the soil tbr the purpose of cuhure~ even over a grave, is destructive of repose.

Nevertheless, as the custom of planting flowers o~ graves, is com- mon throughout Europe , and of planting them in beds is frettuent in the cemeteries about L o n d o n , arrangements for this purpose must b(: provided accordingly. -We would never plant flowers or flewerit~g shrubs in the margins of masses or belts, or in beds or patches that might be mistaken for those of a lawn or a flower-garden; but, to give them a distinctive character, we would plant them in beds of the shape of graves or coffins, raised above or sunk beneath the general snr[kce, and oniy it~ si tuat ions and on spots where at some future time a grave wou lc /be dug. For example, two graves are seldom dug dose together, bu t an intervening piece of firm ground is always left of width sufficient for forming a grave at a future time : the object being to have, if possible, at all times, firm ground f~)r the' sides of ;~ grave which is about to be excavated. Now, ou these intervenir~g- spots alone would we plant beds of flowers, or of roses, or of other flowering shrubs. %then flowers, shrubs, or trees are t)lanted on oc- cupied graves, it is done by individuals according to ttieir own taste. The most highly o rnamen ted cemetery in the neighborhood of London, as Nr as respects p lants , is that of Abney Park, in which as already mentioned, there is a complete aboretum, including all the hardy kinds of rhododendrons, azaleas, and roses in Messrs. Loddiges' col- lection; and in w h i c h also dahlias, geraniums, fuchsias, vebenas, peturfias, &e., are p lan ted out in patches in the summer season.

To be Continued.

f)esc~,~i])fior~ o f f•e Roodf~" over Buckinxf~ara Palace, covered wit[~ Lo~'d ,S'[:a~/~ope's eomposifion. By Pn'r~R HoG% Assoc. Inst. C. E.

The mixture i~veute(t by Lord Stanhope, and used by the late 5~r. Nash, for covering the nearly flat fire-proof roofs of Buckingham Palac% is described in the paper as being composed of Stockholm tar, dried etlalk in pow de r , and sifted sand, in the proportions of three gallons of tar, to t w o bushels of chalk, and one bushel of sand, the whole being well boiled and mixed together in an iron pot. It is laid on in a fluid state, ill two separate coats, each about three-eighths of an i~ch in thiekr~ess, squared slates being imbedded in the upper tea b allowing the mix tu r e to flush up between the joints the whole thickness of the two coats, and the slates being about an inch. The object m imbedding the slates ir~ the composition, is to prevent its

Description oa t. the I~oof~ over Buelelngham Palace. 99

becoming softened by the l'teat of the sun, and sliding dmvn to the lower part of the rooi) an inclination being given of only 1~ inch in Io feet, which is sufficient to carry off the water, when the work is carefully executed. One gutter, or water-course, is made as near to the centre as possible, in order to prevent any tendency to shrink from tile wails, and also that the repairs, when required, may be more readily eifected. It is stated, that after a fall of snow it is not neces- sary to throw it fi'om the roof, but merely to open a channel along the water-course, and that no owq'llowing has ever occurred; whereas, with metal roof~ it is necessary to throw of[' the whole of the snow ot~ the first indication of a thaxv. These roof~ have been found to prevent tile spreading of fires, and it is stated, that on one occasion, to test their uniuflammability, Mr. Nash had a bonfire of tar barrels lighted on the roof of Cowes castle. Another advantage is stated to be the facility of repair which the composition offers, as if a leak oc- cm's, it can be seared and rendered perfectly water-tight, by passing a hot iron over it ; and when taken up, the mixture can be remeltcd and used again. The author proposes to obviate tile disadvantage of the present weight of these reelS, by building single brick walls at given distances, to carry slates, upon which the composition should be laid ; instead of filling tile spandrils of the arches with solid mate- rials, as has been hitherto the custom.

The reported thilures of this species of eovering at Mr. Nash's house in llegent street, and in other places~ are accounted [br by the cornpositiorl having been used in one thin coat, laid upon an impro- per tbundation of laths and tiles. The durability of the roofs, which were carefully constructed with good materials, has been, it is con- tended, fully proved at Lord Pahnerston's house, which was covered with the composition in 1807 ; Lord 13erwiek's, in 1810; Sir James Langham's, in 18t2; the Pavillion, at Brighton, in 1816 and 1823; and nearly thc whole of Buckingham Palace, in 1826 and 1829; /he latter roofs are stated to be in perfect order at; the present time, and have scarcely demanded arty repairs since their completion.

Remarles.~Mr. Poynter presented a drawing of the mode of set- ting the pots for melting and preparing the composition, the p [o p o f tions of which he stated somewhat differently from those given m the paper. Thrcc measures of ground chalk, dried and sifted very fine, were mixed and kneaded up with one measure of tar ; these ingre- dients were melted in an iron pot, set iu such a manner that the flame should not impinge too violently upon it. The first or "skimming' ' coat of the covering being laid on of a thickness of -2~- inch, the fin- ishing coat was composed, by adding to the tormer mixture, three measures of' hot sified sand, well mixing tile whole together; the composition was laid on with a tool similar to a plasterer's trowel, but much stronger. Mr. Nash, when he first tried the composition, found that the surtitce became disintegrated by exposure to the weather ; he, therefore, added the slates imbedded in the second coat, and sub- sequentiy never used the mixture without them.

Mr. Nixon, in reply to questions from the President and other members, stated, that he was employed under Mr, Nash when the

100 Mechanics and Chemistry.

palace roofs were executed, and he could bear testimoay to their dnrability and soundness. The roofs at East Cowcs castle, which were covered with ~he composition in the year 18o8, and tlmse of the Pavitlion, at 13righton, in 1816~ were now in as ~ood a state as when they were finished. The failure at Mr. Nasl{~s house, in Regeat s~reet, arose from the roof having been originally composed of mastic, which soon cracked. One coat of the Stanhope composition was spread over it, to stop the leaks, bttt it was insutticient~y done, and ultimately Mr. l{ainy bad a new roof, properly col~struetcd, with two coats of composition, which had remained sound to the preseut time. The price of these roof~, when welt constructed by the persotl who did those of the palace,* was abotlt five guineas per square.

Mr. I ioggobscrved, that the chalk was onty exposed to such a heat as would evaporate any II-loisttlro it contained. The weight of tile two coats of Stanhope composition, including the slate imbedded in it, was about 12 lbs. per superficial foot.

Mr. Siblcy considered the Seyssel Asphalte, when carefully laid, prctbrable to any comf)osition of a similar tmtnre; he had used it extensively, and was well saltsiied with it, botl~ for roofing and paving.

Mr. lIoe~: "~ objected to the use o[' asphalte fbr roofing,, as it was liable Io injm T, being of a brittle nature; it was not elastic, and it sl:n'unlc from the walls, thercby causing leaks. Lord SmnhOlm"s eompositim~ did not possess these faults~ and he (lid I~ot con,~ider that it was super- seded by asphatte.

Mr. Moreland had covered the roof of the tread-mill, at Oiltspur Street Compter, with aspha/te, and had found it answer perfectly. It was laid on in a thickness of g inch upon roofing boards ~ inch thick, with canvas nailed on them, with an entire fall of only 9 inches; there was not any appearance of leakage.

Mr. I)avidson had caused a school-room to be floored with asphalte, tbur years ago, and np to the present time, there was no symptom of wearing down, although the stones which were let into the floor, for supporting the desks, &c., were eonsiderabiy abraded, He believed that the only failures of the asphalte had occurred from the use o f inferior ingredients. Gas tar had been used instead of vegetable tar~ and in those eases the result had not been successful.

Civ. Eng. &. _&reh. Jourm

~ l e c h a n i c s a n d C h e m i s t r y .

]fOR T | f ~ J O U R N X L OF ~Ett~; F R A N K L I N I N S T I T U T E .

0~ t/be Strength o f C~llindr@al .Boilers. By THomAs VV. BA~E- W~LL~ Esq.

A eommunieation from me on the above subject, appeared in the January number of this journal. Prompted by a report on the ex- plosion of a boiler in the steamboat Medora, and composed by Mr,

* Mr. MiUscn, No. 6 Frances Street, Tothill Fields, Westminster.