VOL.8, NO. 3
EXPERIMENTAL VACUUM OVEN
555
temperatures special wiring of the space heaters would be supplied to avoid wasted energy in the rheostat. The two wirings discussed above have the distinct advantage that they provide a symmetrical distribution of the heat within the oven which is a distinct advantage. Discussion of General Operating Conditions By the use of the apparatus described temperatures constant to *3"C. can be easily maintained over long periods of time even with the average fluctuation in line voltage of the commonly employed power line. With sources of power controlled to avoid changes in voltage, temperatures of smaller variation could be easily obtained. The vacuum realized using a moderate capacity vacuum pump (such as the Mega-Vac) was found to be from 1-3 mm. Shutting off the vacuum pump from the oven a t such pressures showed a maximum leakage of 0.5 mm. per hour and oftentimes less. Opening and closing the vacuum chamber repeatedly does not alter the possibility of attaining an equally low vacuum. The estimated cost of the equipment designed as described is thought to be less than one hundred dollars including material and workmanship.
Cottonseed Meal Used a s Fish. Feed. Although few fishermen would care to bait their hooks with a string of cotton seeds, it has just been found in the animal nutrition laboratory of Carnell University that cottonseed meal is one of the most satisfactory of the plant products for rearing brook trout. The meal cannot be fed alone hut is mixed in equal parts with dry skim milk and a good fish meal. This dry feed is made into a paste with water and combined with a small amount of raw meat before the fish dietitian casts it to the hungry trout. Among a great many plant foods which have been studied, cottonseed meal excels. In contrast to cottonseed meal linseed meal is very toxic to brook trout. I t will kill them in a few weeks although they are capable of living without any food for several months.-Science Serwice
Chemistry Influeneed Whistler's Career. James Abbott McNeill Whistler, the famous painter, told how chemistry influenced his career. When a young man, Whistler was enrolled a t the United States Military Academy a t West Point. He was having trouble with his studies in general and chemistry in particular. I n a chemistry examination Whistler was asked: "What is silicon?" He answered. "Silicon is a gas." West Point record: Jones Whistler, discharged J m e 16, 1854, for defidency in chemistry. Many years later when Whistler had achieved international fame as an artist, he remarked. "If silicon had been a gas, I would have been a major general."
