French Paste Diamonds.
There are a dozen different methods of making artificial diamonds, but none of the stones produced by these methods can compare with those made of old French paste, the secret of which is lost. So perfect were paste diamonds that it was difficult for even a person with expert knowledge of diamonds to tell that they were artificially produced, whereas most of the modern artificial diamonds can easily be detected, and their durability is nothing like so great as the old paste diamonds; indeed, good paste diamonds are now almost as valuable as real diamonds.
Probably not one out of every ten thousand buildings standing in all parts of the world and built by modern masons will still be standing five hundred years hence. We do not know how to put stones and bricks together as the ancients did, and consequently the buildings we raise nowadays are really mere temporary structures, and will be in ruins when the ancient buildings of Greece and Italy, which were built thousands of years ago, are in as good condition as they are now.
The secret is not in the bricks or the stone, but in the cement and mortar, neither of which essentials can we make as the ancients made them.
In modern buildings the cement and mortar are the weakest points; in the buildings which the Romans and Greeks raised thousands of years ago the cement and mortar are the strongest points, and hold good while the very stones they bind together crumble away with age. We cannot, with all our science, make such cement and mortar, and therefore we cannot build such buildings as the ancients raised.