June 14, 1873.] 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
997 
small tube, surrounded by jets of steam, as from concen¬ 
tric rays of an argand burner. Whilst your reporter was 
present, a delicate and somewhat intricate cast-iron pattern 
was laid upon a piece of marble. The steam in the boiler 
was at 55 lbs. pressure. In five minutes the marble, mea¬ 
suring 13 inches by 6, was penetrated to a depth of about 
3-16ths of an inch, leaving the surface as originally 
polished, and with the beautiful tracery design in high 
relief. The sand is ordinary silver sand, and was used at 
the rate of one pint per minute ; the slab of marble was 
three-quarters of an inch in thickness, and was rapidly cut 
by the sand blast, and so separated from a larger piece. 
“ This eroding action of sand mixed with water has 
formed many of the ravines and glens in our island. If the 
following statement, made to the writer of this report about 
ten years ago, be true in fact, there is a property in water 
which has not yet been utilized. Whilst standing near a 
new steam-boiler which was being tested under water 
pressure, and when the load was near its maximum, a 
small and (except that the sun shone upon it so that the 
light was decomposed) imperceptible jet appeared ; the 
writer was about to pass his finger across it, when a work¬ 
man said, ‘ Don’t do that, sir; a boy had his finger cut 
off with one of those jets.’ Might not a jet of water be 
used as a saw ?” 
With reference to the remark in the last paragraph as 
to the part this eroding action of sand mixed with water 
has played in affecting the physical features of this 
country, it will be interesting to quote from the lecture 
“ On Niagara,” recently delivered at the Royal Institu¬ 
tion, by Professor Tyndall, some remarks as to the genesis 
and proximate destiny of those falls :— 
“ Time and intensity are the main factors of geologic 
change, and they are in a certain sense convertible. A 
feeble force acting through long periods, and an intense 
force acting through short ones, may produce approxi¬ 
mately the same results. To Dr. Hooker I have been 
indebted for some samples of stones, the first examples of 
which were picked lip by Mr. Hackworth on the shores of 
Lyell’s Bay, near Wellington, in New Zealand, and des- 
scribed by Mr. Travers in the ‘ Transactions of the New 
Zealand Institute.’ Unacquainted with their origin, you 
would certainly ascribe their forms to human workman¬ 
ship. They resemble flint knives and spear-heads, being 
apparently chiselled off into facets with as much attention 
to symmetry as if a tool guided by human intelligence 
had passed over them. But no human instrument has 
been brought to bear upon these stones. They have been 
wrought into their present shape by the windblown sand 
of Lyell’s Bay. Two winds are dominant here, and they 
in succession urged the sand against opposite sides of the 
stone ; every little particle of sand chipped away its in¬ 
finitesimal bit of stone, and in the end sculptured these 
singular forms. 
“ The Sphynx of Egypt is nearly covered up by the 
sand of the desert. The neck of the Sphynx is partly cut 
across, not, as I am assured by Mr. Huxley, by ordinary 
weathering, but by the eroding action of the fine sand 
blown against it. In these cases nature furnishes us with 
hints which may be taken advantage of in art ; and this 
action of sand has been recently turned to extraordinary 
account in the United States. When in Boston, I was 
taken to see the action of the sand-blast. A kind of 
hopper, containing fine siliceous sand, was connected with 
a reservoir of compressed air, the pressure being variable 
at pleasure. The hopper ended in a long slit, from which 
the sand was blown. A plate of glass was placed beneath 
this slit, and caused to pass slowly under it ; it came out 
perfectly depolished, with a bright opalescent glimmer, 
such as could only be produced by the most careful grind¬ 
ing. Every little particle of sand urged against the glass, 
having all its energy concentrated on the point of impact, 
formed there a little pit, the depolished surface consisting 
of innumerable hollows of this description. But this was 
not all. By protecting certain portions of the surface and 
exposing others, figures and tracery of any required form 
could be etched upon the glass. The figures of open iron¬ 
work could be thus copied ; while wire gauze placed over 
the glass produced a reticulated pattern. But it required 
no such resisting substance as iron to shelter the glass. 
The patterns of the finest lace could be thus reproduced ; 
the delicate filaments of the lace itself offering a sufficient 
protection. A fraction of a minute suffices to etch upon 
glass a rich and beautiful lace pattern. Any yielding 
substance may be employed to protect the glass. By 
immediately diffusing the shock of the particle, such sub¬ 
stances practically destroy the local erosive power. The 
hand can bear without inconvenience a sand-shower which 
would pulverize glass. Etchings executed on glass with 
suitable kinds of ink are accurately worked out by the 
sand-blast. In fact, within certain limits, the harder the 
surface, the greater is the concentration of the shock, and 
the more effectual is the erosion. It is not necessary that 
the sand should be the harder substance of the two ; 
corundum, for example, is much harder than quartz ; 
still, quartz-sand can not only depolish, but actually blow 
a hole through a plate of corundum. Nay, glass may be 
depolished by the impact of fine shot ; the grains in this 
case bruising the glass before they have time to flatten 
and turn their energy into heat. 
“ And here, in passing, we may tie together one or two 
apparently unrelated facts. Supposing you turn on, at 
the lower part of a house, a cock which is fed by a pipe 
from a cistern at the top of the house, the column of water, 
from the cistern downwards, is set in motion. By turning 
off the cock, this motion is stopped ; and when the turn¬ 
ing off is very sudden, the pipe, if not strong, may be 
burst by the internal impact of the water. By distribut¬ 
ing the turning of the cock over half a second of time, 
the shock and danger of rupture may be entirely avoided. 
We have here an example of the concentration of energy 
in time. The sand-blast illustrates the concentration of 
energy in space. The action of flint and steel is an 
illustration of the same principle. The heat required to 
generate the spark is intense, and the mechanical action 
being moderate, must, to produce fire, be in the highest 
degree concentrated. This concentration is secured by 
the collision of hard substances. Calc-spar will not supply 
the place of flint, nor lead the place of steel in the pro¬ 
duction of fire by collision. With the softer substances, 
the toted heat produced may be greater than with the 
hard ones, but to produce the spark, the heat must be in¬ 
tensely localized. 
“ This power of erosion, so strikingly displayed when 
sand is urged by air, renders us better able to conceive 
its action when urged by water. The erosive power of a 
river is vastly augmented by the solid matter carried 
along with it. Sand or pebbles caught in a river vortex 
can wear away the hardest rock; ‘ potholes ’ and deep 
cylindrical shafts being thus produced. An extraordinary 
instance of this kind of erosion is to be seen in the Yal 
Tournanche, above the village of this name. The gorge 
at Handeck has been thus cut out. Such waterfalls 
were once frequent in the valleys of Switzerland; for 
hardly any valley is without one or more transverse bar¬ 
riers of resisting material, over which the river flowing 
through the valley once fell as a cataract. Near Pon- 
tresina, in the Engadin, there is such a case; the hard 
gneiss being now worn away to form a gorge through 
which the river from the Morteratsch glacier rushes. 
The barrier of the Kirchet above Meyringen is also a 
case in point. Behind it was a lake derived from the 
glacier of the Aar, and over the barrier the lake poured 
its excess of water. Here the rock, being limestone, was 
in great part dissolved; but added to this, we had the 
action of the sand particles carried along by the water, 
each of which, as it struck the rock, chipped it away like 
the particles of the sand-blast. Thus by solution and 
mechanical erosion the great chasm of the Fensteraar- 
schlucht was formed. It is demonstrable that the water 
which flows at the bottoms of such deep fissures once 
flowed at the level of what is now their edges, and turn- 
