Our plans were suddenly ruined. A change in the method of facing ashlar was introduced and soon became universally adopted. Instead of being faced by hand, it began to be sawn out of large blocks. I have since wondered why this had not been done long before. Blocks of marble had been sawn into slabs by gang-saws no one knows how long, and all that had to be done was to apply the same system to blocks of building-stone. It was found to cost no more to saw ashlar than it had done to split it out at the quarry. All the cost of facing and much stone were saved. Our stone-cutting machine became useless, and I learned that disappointments were not confined to the legal profession.
The speed of 300 revolutions per minute had proved to be admirably suited for the machine. Familiarity with this speed in the running of the stone-dressing machine made me alive to the value of high rotative speeds in all cases to which they are adapted.
In looking back over this period I see that the success of the stone-dressing machine was due to the following causes:
First, I went about the work of facing stone by machinery in the natural way.
Second, the machine was superabundantly strong and substantial in every part.
Third, it was made with absolute mechanical truth.
Fourth, the speed was splendid.
Fifth, the blow was peculiar. In the Hastings machine the cutting-tool was driven into the stone. In mine it rested on the stone and was moved back horizontally by the feed. This changed slightly the angular position of the tool-holder, so that the blow was received by it at the lower edge of its back. This gave to the tool a motion forward and upward, so that the vertical effect on the stone was trifling.
This was the vital feature of my improvement, and that in a double sense; for it was only by convincing my associates beforehand that a machine operating in this manner could not break the stone that I was able to obtain their financial support.
Sixth, the two-faced hammer saved the stone from all unnecessary force of the blow.