Calcareous tufa is formed when waters which contain carbonic acid gas and lime carbonate in solution, give off the gas and with it the power to hold the lime in solution.
Footnote D: The volcanic rocks are the Tufa litoide, very hard, and used for paving and other such purposes; difficult to be quarried, and unfit for graves on account of this difficulty.
In such cases the tufa may have been broken down into the condition of sand for removal.
The deposit of tufa is covered by a sheet of 'loess' corresponding with the return of an arid period in late Acheulean times, in the very heart of northern France.
In the tuf de La Celle-sous-Moret the layer of 'loess' immediately overlies the tufa layer containing late Acheulean implements and proofs of a cooler climate.
We have already shewn that tufa is not of ancient formation, and must not be ranked in the class of stones.
Palagonite, exactly similar to that of Iceland or in Italy, was discovered by Bunsen in the specimens of tufa from Chatham Island, one of the Gallipagos.
Cyrus Harding felt the volcanic tufa with which the plain was strewn, and which were but pulverised cinders hardened into solid blocks by time, tremble beneath him, but he could discover no traces of fresh lava.
Fortunately, this cone inclined to the north, and had fallen upon the plain of sand and tufa stretching between the volcano and the sea.
Here he found a little soil covering a limelike tufa deposit.
When these salt deposits occur in a flat country with a tufa layer covering the soil, a chemical change takes place in the soil; the tufa is dissolved and the ground kept in a state unfavorable to the growth of plants.
This bed of tufa in the Zambesi region is more or less hardened, according to the exposure it has had to atmospheric changes.
Rousteaux’s cellars here are excavated in the tufa cliff which rises behind the little suburban village, and are all on one level.
In the upper layers of the tufa we find far better pottery decorated in the Phenician style.
Then they came to a layer of solid tufa two feet thick, then one foot of muck in which they found another log.
Below the rocks the workmen followed the spring through four feet of tufa and muck.
It is only when lavas are covered with tufaand ashes, that the volcanic islands, losing that appearance of nudity which marks their origin, bedeck themselves in rich and brilliant vegetation.
Teodoro are remains of an early concrete wall, behind which the tufa rock is visible.
From hence we can look down upon some grand walls of republican times, formed of huge tufa blocks.
Tomb of the Scipios, a small catacomb in the tufa rock, discovered in 1780, from which the famous sarcophagus of L.
It is built in the Etruscan style, of huge blocks of tufa or peperino placed long-and cross-ways alternately.
The wall is only built where the tufa is of a soft character.
But even whentufa was used for the reticulated work, bricks or tiles were used for quoins at the angles, and for bonding courses through the walls, as well as for arches and vaults (Fig.
A mass of the cretaceous tufa has slipped bodily down to the foot of the crag, against which it leans in an inclined position.
The face of the mountain is precipitous, and is of a porous tufa full of holes.
Formerly a barrier of volcanic tufa stretched across the valley of the Borne; this barrier had been ejected from the volcano of La Denise.
The Tuscan stone is softer in quality than tufa but harder than earth, and being thoroughly kindled by the violent heat from below, the result is the production in some places of the kind of sand called carbuncular.
In red tufa it is copious and good, if it does not run down through the fissures and escape.
So the fire and the heat of the flames, coming up hot from far within through the fissures, make the soil there light, and the tufa found there is spongy and free from moisture.
In the narrow descent that led to it Mr. Wood showed me in three consecutive strata the tufa of the time of the kingdom, travertine of the republic, and brick of the empire.
From San Bartolome to Comitan, the road passes over a curious lime deposit, apparently formed by ancient hot waters; it is a poroustufa which gave back a hollow sound under the hoofs of our horses.
Where there was not sufficient water to produce a stream and fall, but enough to keep the tufa moist, the growth of ferns, and other delicate vegetation, was brilliant and striking.
The subsoil too is differently formed: the surface consists of very absorbent materials, then comes a stratum of less permeable tufa or peperino (sometimes clay is present), and below that again more permeable materials.
From beds underlying the lava and volcanic tufaof California, from time to time other evidences of the assumed ancient presence of man and traces of his art are produced.
It covers the bottom of the valleys between low terraces, covered with faceted pebbles, and dominated by the vertical cliffs of tufa and lava.
Below the higher slopes the valleys deepen into gorges, and these broaden out in the soft tufa and are lost at the cross-streams of lava or the outcrops of the granite.
Many of them are cut in full relief out of the tufa and are always in some natural attitude, and can always be identified where the weather has not destroyed the original form.
Many small square rooms were constructed in the interior from large cut bricks of the tufa of which the bluffs are composed.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "tufa" in a variety of sentences. We hope that you will now be able to make sentences using this word.
