GAIETY - Mr. W.S. Gilbert appears fond of classical subjects, and certainly treats them with skill.  He has given us, at the Gaiety, "an original grotesque opera," and brought "Thespis" on the boards, in the person of Mr. Toole, who undertakes to manage the globe as he would a theatre.  In the first act we have for the scene a ruined temple of the gods on Mount Olympus, for the deities, grown old, have sadly neglected matters; in the second we have the same temple restored.  Our Illustration represents the gods in their senility.  Jupiter has taken to spectacles, and Mars is rather inclined to take his ease.  Mercury alone (Miss E. Farren) is still lively and active, but finds that the superior intelligences leave him all the work to do.  The part suits Miss Farren admirably; she keeps the stage in a perpetual bustle, and drives on the action with an impetuosity which startles and surprises the audience and renders occasional slumber impossible.  The authority of the gods being deputed to Thespis, they, all but Mercury, are free to disport themselves on earth and learn something more of mankind than they have hitherto been acquainted with.  One twelvemonth is sufficient to show the incapacity of Thespis and his company.  Mercury is burdened with scrolls containing the complaints of mortals, and such is the proved condition of things that the ancient authorities have to resume their dominion in order to repair the errors of their substitutes.  Much of the dialogue suggests thought, and there is an amount of concealed satire which is none the less pointed for being sheathed.  It is gratifying to find that such a subject, so treated, can be attractive to modern audiences.