ON AN EXPERIMENTAL INVESTIGATION INTO THE FLOW OF MARBLE. 371 
but it was found that none possessed a sufficiently high elastic limit combined with 
the required ductility, except certain aluminium bronzes, which however it was 
difficult to obtain with constant composition and properties. Heavy tubes of wrought 
iron were then made on the plan adopted in the construction of ordnance by rolling a 
thin strip of Low Moor iron around a bar of soft iron and welding the strip to the bar 
as it was rolled around it. The core of soft iron composing the bar was then bored out, 
leaving a tube of welded Low Moor iron, the sides being about a quarter of an inch 
thick, and so constructed that the fibres of the iron ran around the tube instead 
of being parallel to its length. These were found to answer the requirements 
admirably. The following procedure was then adopted : Columns of the marble, 
0*81 inch, or in some cases 1 inch, in diameter and 1*58 inch in length, were 
accurately turned and polished, by Messrs. Voigt and Hochgesang, of Gottingen. 
The tube was then very accurately fitted around the marble'. This was accomplished 
by giving a very slight taper to both the column and the interior of the tube,. and so 
arranging it that the marble would only pass about half way into the tube when cold. 
The tube was then expanded by heating, so as to allow the marble to pass completely 
into it and leave about 1*25 inch of the tube free at either end. On allowing the 
tube to cool a perfect contact between the iron and marble was obtained, and it was 
no longer possible to withdraw the latter. This perfect fit was considered indispens¬ 
able in order to prevent the limestone crumbling when pressure was applied, as it 
would have done had it not been supported at every point. In some experiments 
the tube was subsequently turned down, so as to be somewhat thinner immediately 
around the marble. Into either end of the tube containing the column an accurately 
fitting steel plug was then inserted, and by means of these the pressure was applied. 
The high pressure required was obtained from the city water mains by using a double 
hydraulic “ intensifier ” ; the whole arrangement being shown in the accompanying 
photograph (Plate 22, fig. 1). 
A cylinder containing a moveable piston, whose upper portion is cast of square 
shape so as to form a press plate, has another press plate mounted opposite to it by 
means of four strong steel columns. The small cylinder containing the marble with 
the two steel plugs is set up between the two press plates, the plugs being kept in 
axial alignment with each other by having then* enlarged ends fitted into cylindrical 
holes bored in a small but massive casting (A), which acts as a guide to them when 
under pressure. The sliding piston in the large cylinder is 20 inches in diameter, 
and is kept tight by cup leather packing. The strong copper vessel (B) has its upper 
half filled with a heavy oil, and thence is led the only pressure connection to the 
cylinder (C), to which oil, but no water, is admitted, in order that corrosion and 
undue leakage may be averted. For moderate pressures the city mains are con¬ 
nected directly to the lower half of the copper vessel, but for high pressures to the 
larger end of the small intensifier (D), and a pipe then leads from the upper end of 
the same to the lower end of the copper vessel. In either case the pressure is kept 
3 b 2 
