_Curious Fact in Natural Philosophy_ (Vol. vii., p. 206.).--In Young's _Natural Philosophy_ it is said, that if the cup of a barometer is placed in a vessel somewhat larger than the cup, so contrived that the tube of the barometer may fit air-tight in the top of the vessel, and if two holes are made in the vessel on opposite sides, a current of air driven in at one hole will cause the mercury to fall. Is not the case of the cards analogous to this? and might not the cause be, that the current of air carries away with it some of that contained between the cards, and so that the air is sufficiently rarefied to cause a pressure upwards greater than that caused by the current downwards, and the effect of gravity? Might not the sudden fall of the barometer before storms be from a cause similar in some degree to this? A. B. C. Oxford. "_Haud cum Jesu itis, qui itis cum Jesuitis._"--In "N. & Q." for Feb. 7, 1852, a correspondent, L. H. J. T., asks for some clue to the above. Last March a friend of mine purchased in Paris, at a book-stall on the Quai D'Orsay, a manuscript book, very beautifully written, and in the old binding of the time, which appears to be the transcript of a printed volume. Its title is _Le Jésuit sécularisé_. A Cologne: chez Jacques Milebram. 1683. It is a dialogue between "Dorval, abbé et docteur en th^e, et Maimbourg, Jésuit sécularisé;" and at the end (p. 197.) is a long Latin ballad, entitled "Canticum Jesuiticum," filling eight small 8vo. pages, the opening stanza of which is "Opulentas civitates Ubi sunt commoditates Semper quærunt isti patres." And the conclusion of the whole is, in effect, the line of which your correspondent speaks: "Vita namque Christiana Abhorret ab hâc doctrinâ Tanquam fictâ et insanâ. _Ergo_ Vos qui cum Jesu itis, Non ite cum Jesuitis." I should be glad to be certified by any of your correspondents of the actual existence of the printed volume, which probably was sought for and destroyed by the authorities on account of its pestilent contents. C. H. H. Westdean, Sussex.