Chap. VI.

PISE.

725

CHAP. VI,

OF PISE.

This method of construction is far more simple than that where unburnt bricks are em-ployed, and by no means so costly ; it is universally adopted in the departments of the Ain ,Rhone , and Isere , in France , and forms fire-proof houses, far preferable for cottages totimber framing, and well suited for barns, stables, or sheds attached to a farm.

Walls properly carried up in this material form one entire mass, and covered with a finecoat of plaster will endure for ages, and present an agreeable appearance. Rondelet informsus that he repaired, in 1764, an ancient chateau in the department of Ain , which hadendured for upwards of 500 years, and that the walls had attained a hardness and com-pactness equal to ordinary stone; when desired to increase the size of the windows andother apertures, the workmen were obliged absolutely to use the same tools as in a quarry.

The Romans practised this system at a very early period in Gaul, and we find men-tion made of it by Pliny , who in admiration observes : “ What shall we say, do we notsee in Africa and in Spain walls of earth called formacei> having the form given to themby planks and boards placed on each face : and between which prepared earth has beenrammed ? The earth so rammed, I can assure you, does continue for years in an imperishablestate, and is neither affected by the beating rain, by wind, nor by fire, and neither mortarnor cement is used in them. In various parts of Spain we see the high watch-towers builtby Hannibal, upon the summits of mountains, with this material.”—Pliny , lib. 35. cap. 14.

Manner of making Pise _The ants probably suggested the process of preparing earth for

building purposes, and in the tropical climates we discover these industrious insects almostrivalling man in the arrangement and strength of their habitations: the elevation of theirhouses exceeds in height 500 times that of the builders. The termites, which are scarcelya quarter of an inch in size, pile up dwellings 7 feet high, and sometimes as much as 20.Rishop Ileber describes some in India which were as much as 7 or 8 feet in circumference;within were numerous galleries and cells, the principal of which was occupied by the kingand queen, placed nearly in the centre; its floor was more than 1 inch in thickness, formedof clay, and the roof one solid well-turned oval arch of considerable strength.

The Termes mordax and Atrox, or turret-building ants, form their habitations witha well-tempered black earth, often 3 feet in height, in form of a conical mushroom :all the varieties of ants select a fine clay for their cells, galleries, and bridges ; liningtheir rooms with a composition formed of wood and gum, which these insects seem tohave the instinct to prepare in a very fine state, and to lay on like a coat of cement;thus it is that man may receive instruction from a close observation of the habits of theanimal creation. All earth is suited for pise-work, but the best is clay which containssmall gravel, and of such a consistence that it can be dug with the common spade:every kind of earth that will sustain itself, with a small slope, is adapted for the purpose,and may be successfully used. To prepare it, after beating thoroughly, it must be passedthrough a screen to take away the stones beyond the size of a common hazel nut; andif not moist it must be watered, and turned over with a shovel until it has acquired aregular consistence, which is known by moulding it by the hand, or between the fingers,and then throwing it into a vessel, when, if it retains the shape given to it, it may beconsidered as fit for use. After the earth is thus prepared, it is put into a frame or move-able box, where it is forced down and beaten with a rammer. 'There is some attentionnecessary for the construction of this box, which is formed of deal planks put together, withtheir joints ploughed and tongued, and further strengthened with clamps on the outside,fastened on with clenched nails. These sides or frames rest, when in their places, oncross-pieces or putlocks, which pass entirely through the thickness of the wall; near theends are mortises, into which upright pieces are placed, wedged firmly at the bottom up tothe sides, already set, to the distance which is to constitute the thickness of the wall,usually about 20 inches at bottom, and gradually diminished as the height is increased;the diminution or inclination is uniform throughout, and in a house of two stories does notexceed 1 foot. The sides or frames are made 10feet in length, and 3 feet high; the uprights5 feet long, comprising the tenons, so that they stand up sufficiently above the sides to allowof being secured by ropes. The wedges are 9 inches in length, 1^ at the base, and 20inches at top, made to fit the mortises exactly, which should be deep enough to permitthe bottom to be 2 inches below that of the wall, that the frame may hold within it aportion of the wall already made. The frames at top are steadied by small sticks, which

3 a 3