The libretto of _La Pietra del Paragone_ is founded on an idea at least as old as that of _Timon of Athens_. Count Asdrubal, surrounded by friends and beloved by a charming young lady, is rash enough to wish to know whether the friendship and the love he seems to have inspired are due to himself and his own personal qualities, or to the riches he is known to possess. To determine the point he causes a bill of exchange for a large sum to be presented at his house. He himself appears in disguise to claim the money; and, in accordance with instructions given beforehand, the count's steward recognises the signature and honours the draft. The sum for which the bill has been made out is so large that to pay it the count's exchequer is absolutely drained. Some few of the friends stand the test well enough, but others, as might have been expected, prove insincere. As for the young lady, the "touchstone" has the effect of bringing out her character in the brightest colours. Timid by nature, she had hitherto refrained from expressing, except in the most reserved manner, the love she really entertains for Count Asdrubal. After his apparent ruin, however, the advances are all from her side; and she finds herself obliged to resort to all kinds of devices in order to compel him to a formal declaration. She even feels called upon to appear--though whether for logical or merely for picturesque reasons can scarcely at this distant date be decided--in a Hussar uniform; and in this striking garb Madame Marcolini sang the celebrated final rondo, saluting the public with her sabre in acknowledgment of their applause, and repeating the salutes again and again as the applause was renewed.