ALDEBARAN--War, as a paying concern, ceased in 1967. (2) The Convention of London expressly reserves to every nation the right of waging war so long as it does not interfere with the world's traffic. (3) The A. B. C. was constituted in 1949. L. M. D.--Keep her dead head-on at half-power, taking advantage of the lulls to speed up and creep into it. She will strain much less this way than in quartering across a gale. (2) Nothing is to be gained by reversing into a following gale, and there is always risk of a turn-over. (3) The formulae for stun'sle brakes are uniformly unreliable, and will continue to be so as long as air is compressible. PEGAMOID--Personally we prefer glass or flux compounds to any other material for winter work nose-caps as being absolutely non-hygroscopic. (2) We cannot recommend any particular make. PULMONAR--For the symptoms you describe, try the Gobi Desert Sanitaria. The low levels of the Saharan Sanitaria are against them except at the outset of the disease. (2) We do not recommend boarding-houses or hotels in this column. BEGINNER--On still days the air above a large inhabited city being slightly warmer--i. e., thinner--than the atmosphere of the surrounding country, a plane drops a little on entering the rarefied area, precisely as a ship sinks a little in fresh water. Hence the phenomena of "jolt" and your "inexplicable collisions" with factory chimneys. In air, as on earth, it is safest to fly high. EMERGENCY--There is only one rule of the road in air, earth, and water. Do you want the firmament to yourself? PICCIOLA--Both Poles have been overdone in Art and Literature. Leave them to Science for the next twenty years. You did not send a stamp with your verses. NORTH NIGERIA--The Mark Boat was within her right in warning you up on the Reserve. The shadow of a low-flying dirigible scares the game. You can buy all the photos you need at Sokoto. NEW ERA--It is not etiquette to overcross an A. B. C. official's boat without asking permission. He is one of the body responsible for the planet's traffic, and for that reason must not be interfered with. You, presumably, are out on your own business or pleasure, and should leave him alone. For humanity's sake don't try to be "democratic." REVIEWS Reviews The Life of Xavier Lavalle (_Reviewed by Rene Talland. Ecole Aeronautique, Paris_) Ten years ago Lavalle, "that imperturbable dreamer of the heavens," as Lazareff hailed him, gathered together the fruits of a lifetime's labour, and gave it, with well-justified contempt, to a world bound hand and foot to Barald's Theory of Vertices and "compensating electric nodes." "They shall see," he wrote--in that immortal postscript to "The Heart of the Cyclone"--"the Laws whose existence they derided written in fire _beneath_ them."