(12533) Y. R. C. asks: In “Heavens in June” in your journal of June 3r d, it was stated tbat we could recognize Venus and Jupiter by tbe fact tbat planets do not twinkle. ThIs I observed to be true. But according to your explanation given in query No. 12461, that distant ligbts twinkle because the strata of tbe intervening air cbange tbeir refractive powers, it sbould not make any difference wbetber the ligbt is from a pl anet or a st ar. Will you please explain i? A. Tbe reason given by astronomers why planets do not twinkle Is tbat they present apparent disks, and are not mere sbinlng points as tbe stars are. Mercury, the smallest planet and tbe nearest to tbe sun, is always seen to be twinkling violently. This peculiarity of Mercury among tbe planets is due to its amaH size, so small tlIat at its great distance from us it has no apparent disk, and its greater intrinsic brightness because of its nearness to tbe sun. See Todd's “New Astronomy,” pages 92 and 313, We can furnisb the book for $l.50. (12534) F. A. C. says: Is it true, as 1 bave often heard stated, tbat dry batteries will give better results (i. e., a better spark at same voltage) than will wet batteries ; bth oatteries being in tbelr best condition. Is this true and wby? A. A dry cell is made to have a very low internal resistance and so to give a large number of amperes on sbort circuit. It tberefore is well adapted to give a very bot spark. If a wet cell were made on tbe same lines it would give tbe same result. It is not tbe voltage of the cell which produces tbis result, but the amperes, and this is tbe quotient of the volts divided by tbe ohms in accordance with Obm's well·known law. (12535) W. L. S, asks: Has an article ever been publisbed in tbe SCIENTIFIC AMERICAN describing a method of hypnotizing one's self and rendering one clairvoyant? Also do you know of any source of information that could furnisb tbe desired data? A. We bave bad many valuable articles on bypnotism in our SUE>LEMENT. We name numbers 148, 295, 371, 587, 720, 756, 1047, 1056. We will send tbese papers for ten cents eacb. We can also furnish, you any book published upon tbe subject ; we name Bramwell, “History, Practice, and Tbeory,” $4.50; “Hypnotism,” by Moll, $1.50 ; “Hypnotism, How It is Done, Its Uses and Dangers,” by Cocke, $1.50. (12536) C. R. asks: On the night of August 15tb I observed a meteor in tile southwestern sky whicb bebaved different from' any I ever before saw or beard of. Wben first noticed it appeared a considerable distance to tbe left and above tbe apparent position of the planet Jupiter. At first it followed the usual wide course, going toward tbe big planet across the sky. At the end of the long course the meteor turned sharply npward, its bright wbite light changing to a brilliant orange, quickly vanisbing in a puff of black smoke. Is it customary for meteors to bebave in this way? What was tbe cause of sucb apparent erratic motions? Does the SCIENTIFIC AMERICAN sell any books on astronomy tbat would be worth wbile to tbe novice? If so, give prices , as I want to buy. A. While it may not be said to be customary for meteors to sbow tbe changes sbown by tbe one you describe, still every sort of beba vior is found in tbem. Changing color and vanisolng as it wit h a puff of smoke is not uncommon. We can supply you any book in pri nt upon astronomy. You will find Prof. Todd's book very interesting and accurate. His “New Astronomy,” price $1.50, is widely used as a text book , and bis “Stars and Telescopes,” price $2, is most interesting to anyone who looks at tbe heavens . (12537) H. R, G. asks: Will you please tell me wbat is tbe scientific explanation of the fact that a perso n can be lifted by tbe forefingers of two persons if tbey inbale at the same moment? A. It is safe to say that tbere is no scientific explanation needed for the fact tbat two persons can lift a person by their forefingers. The writer used to Uft 150 pounds with one little finger, and feels no surprise that two persons should lift tbe same weigbt by using four much stronger fingers for tbe purpose. Tbe Inbaling of tbe )reatb diverts the attention of the persons from the t of lifting, and they usually say tbey do not lift at all. But to raise a person weigb· Ing 160 pounds, that weight must actually be lifted, and each finger must lift 40 pounds. Tbis is a sma l l weigbt for a forefinger to lift. We do not tbink tbere is any occult force in action bere, but just a simple action of the muscular force. We bave seen it done witbout any inhalation of breatb at all, and just as easily as w ben lnbaling the breath.