In the latest issue "Stolen Brains" was fine, up to the Dr. Bird standard. "The Invisible Death" was good enough, but too much like the general run to be noteworthy. "Prisoners on the Electron"--couldn't stomach it. Too hackneyed. "Jetta of the Lowlands," by Ray Cummings; nuff said. "An Extra Man"--original idea and perfectly written. One of the reasons I hang on to Science Fiction. A perfect gem.--Philip Waite, 3400 Wayne Ave., New York, N. Y. Dear Editor: May I use enough space in your discussion columns to reply briefly to the objections raised to the science in my two stories, "Beyond the Heaviside Layer" and "The Attack from Space"? Understand that I am not arguing that there actually is a thick wall of semi-plastic material surrounding the earth through which a space flyer could not pass. If I did, I would automatically bar myself from writing interplanetary stories, a thing that is far from my desires. I do wish to point out, however, that such a layer might exist, so far as we at present know. The objections to which I wish to reply are two: first, "How do meteors pass through that imaginary substance which is too much for a powerful space flyer?" and second, "How about refraction?" To reply to the first we must consider two things, kinetic energy and resistance to the passage of a body. The kinetic energy of a moving body is represented by the formula 1/2 mv^2 where m is the mass of the body and v the velocity. The resistance of a substance to penetration of a body is expressed by the formula A f_c where A is the area of the body in contact with the resisting medium and f_c is the coefficient of sliding friction between the penetrating body and the resisting medium. Consider first the space flyer. To hold personnel the flyer must be hollow. In other words, m must be small as compared to A. A meteor, on the other hand, is solid and dense with a relatively large m and small A. Given a meteor and a space flyer of the same weight, the volume of the meteor would be much smaller, and as the area in contact with the resisting medium is a function of volume, the total resistance to be overcome by the space flyer would be much greater than that to be overcome by the meteor. Again, consider the relative velocities of a meteor and a space flyer coming from the earth toward the heaviside layer. The meteor from space would have an enormous velocity, so great that if it got into even very rare air, it would become incandescent. As it must go through dense air, the space flyer could attain only a relatively low velocity before it reached the layer. Remember that the velocity is squared. A one thousand pound meteor flying with a velocity 100 times that of the space ship would have 100^2 or 10,000 times the kinetic energy of the space ship while it would also have less friction to overcome due to its smaller size.