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A Gas Lighter Than Hydrogen ? To the Editor of the SCIENTIFIC AMERICAN : In your article on “Germany as Nature's Competitor “ in the November 20th issue of the SCIENTIFIC AMERICAN, reference is made to the invention of a non-inflammable gas lighter than hydrogen for use in German airships. In an article in Collier's that appeared in the summer of 1914, by Dr. K. A. Graves, on the “ German War Machine,” the author laid great stress on this wonderful invention which he claimed had several times the lifting power of hydrogen. The absurdity of such a claim may be readily demonstrated by a simple calculation. Avogadro's law states that the volume of any gas bears a direct proportion to its molecular weight. Or the volume of a molecule of any gas is equal to the volume occupied by a molecule of any other gas at the same conditions of temperature and pressure. Now, the volume occupied by I pound molecule of any gas at 62 deg. Fahr. and 30 inches Hg. press. is 380 cubic feet, or the volume occupied by 1 pound of any 380 gas at this temperature and pressure is-cubic feet, m -where “m” equals the molecular weight. Furthermore, the lifting power of any gas per unit of volume is equal to the difference between the weight of this volume of air and the weight of the same volume of gas which displaces it. Let us calculate the maximum lifting power of a weightless envelope containing 500,000 cubic feet of hydrogen at 62 deg. Fahr., 30 inches Hg. 500,000 x 28.95 Weight of Air - = 37,700 lbs. 380 500,000 x 2 Weight of Hydrogen--= 2,630 lbs. 380 35,070 lbs. net lifting inconvenience which might result to an inventor from attempting to market, on the basis of a favorable opinion as to patentability, an invention which he afterwards found was not patentable. It was, to say the least, an extremely unfair mode of dealing with a client. A CONSTANT READER. Washington, D. C. Galveston During the Recent Storm To the Editor of the SCIENTIFIC AMERICAN : The exaggerated reports of the injury to the City of Galveston during the recent Texas coast storm were entirely unfounded, as there was little property damage, except to the fill immediately behind the seawall, which was absolutely uninjured and accomplished all that was expected of it. The total death loss was eight persons and the only serious condition confronting the city at any time was the partial destruction of the county's causeway, upon which was one of the city's water mains. All of the expensive archway construction of the causeway is intact and only that concrete portion of the structure which was filled with sand was injured and the concrete sheet piling was entirely undisturbed. The large volume of water rushing through the archway undermined the submerged duplicate water, main which paralleled the causeway and approximately 800 feet of this was put out of commission, so the city was for a few days without water supply. An ingenious experiment was made in inserting 20-inch dredging 'pipes into the broken ends of the 30-inch main and packing the space with ropes and oakum, and wedging with pine wedges. After the wedges were calked with shingles a small cofferdam of cement sacks was made under water and cut open from the inside, and the entire void filled with cement and then rammed by divers until the whole was like a mass of putt^ After waiting 48 hours to allow the cement to set the water was turned on and the experiment was entirely successful. The protective works of Galveston have justified the energy and thrift of her people in building a port whose foreign exports are exceeded only by New York city alone and which ] exceed ten per cent of the foreign exports of the entire United States. Conditions in Galveston are entirely normal, as evidenced by a comparison with August, 1914, wherein the August of 1915, in which month the storm visited the Texas coast, reflects greater bank clearings, larger pay rolls on the wharf front and a larger receipt of cotton. You have evidenced in the past such an interest in the construction of the seawall, designed by General Roberts and Alfred Noble, -also the filling of the city with over 15,000,000 cubic yards of sand, as well as the building of the great jetties by the United States Government, that I hope you can find space to refute the adverse reports condemning one of the greatest ports of this country. GEORGE SEALY, Second Vice-President of the Galveston Commercial Association. Galveston, Texas. Pipe Stems Bored by Larvae To the Editor of the SCIENTIFIC AMERICAN : In your correspondence column, of November 27th, Mr. Hawley, of the Smithsonian Institution, asked for additional information on the boring in wood of long holes by larvae and gives - extract from Mr. Beede's letter on the' Sioux Indians' use of larvae taken from dead ash to drill their wooden pipe stems. I have on my desk a number of oak sticks about the right shape and length for pipe stems which have been bored lengthwise under my observation by the “oak pruner,” or Elaphidion villosum. The twig is cut from the oak tree-by the larva in the early autumn and falls to the ground, carrying the larva in the falling portion. The larva plugs the open end with shavings and lives until . spring on the material which it cuts out of the twig. Usually, but not always, he cuts along the center of the twig and removes all the chips through a special opening in the bark at one point, so that the hole is clean from the plugged end. to the opposite end at which he is working. We have even .X-rayed him at work. These chips are all excrement of the larva. The shavings he makes for plugging the-original first openings -are clearly a special product. In the spring he 'emerges as a blackish, flying beetle, about', % inch long, and soon deposits an egg in the green growing end of a small oak bough, where its presence kills' t):1e original small shoot and the larva later works backward and inside the wood to a larger branch, which he finally cuts from the tree at a point where it is usually between one half and one quarter inch diameter. The hole oval and not far from lh inch diameter. Its length varies from 4 to 10 inches,~in the casesT have seen. W. R. WHITNEY. Schenectady, N. Y.
