858 



THE POPULAR SCIENCE MONTHLY. 



ceptable than red. Mixtures of linseed-oil 

 and gypsum were eaten freely, but not so 

 freely as the whiting mixture. Carbonate 

 of baryta proved to be poisonous to the ani- 

 mals, but the poison seemed to be neutral- 

 ized when carbonate of lime was mixed 

 with it. Carbonate of lead seemed to act 

 as a poison, but not so deadly, provided it 

 was mixed with whiting, as it might have 

 been supposed to be. Clay was not appre- 

 ciated by the mice, but was eaten when 

 mixed with whiting. Experiments with va- 

 rious results were also tried with sulphate 

 of baryta, silica, carbonate and oxide of zinc 

 (both eventually producing death), slaked 

 lime (of which only one of the mice would 

 eat enough to kill him), and whiting and 

 sirup, whiph was eaten freely. Similar ex- 

 periments were tried on rats, with similar 

 results. 



Raittfall as affected by Wind. — The 



proper construction and location of rain- 

 gauges to secui-e measurements agreeing 

 with the average rainfall on the surround- 

 ing district has been a much - discussed 

 problem. In 1766 Dr. Heberden observed 

 that gauges on the ground collect generally 

 a larger quantity of rain than gauges on the 

 sides and roofs of buildings. As a sum- 

 mary of facts since learned, G. E. Curtis, in 

 "Signal-Service Notes," No. 16, quotes the 

 following from an article published by Sy- 

 mons in 1878: "The greater part of the 

 decrease is due to wind. The stronger the 

 wind, the greater the decrease with eleva- 

 tion. The less the diameter of the elevated 

 gauge, the less will it indicate. A gauge on 

 the leeward side of a tower may collect as 

 much rain as one on the ground. A gauge 

 in the middle of a large roof may, notwith- 

 standing its height, collect very nearly the 

 same as one upon the ground." In the fol- 

 lowing year Symons further stated that 

 "there is no evidence of any difference be- 

 tween the fall of rain at various heights 

 from sixty to two hundred and sixty feet 

 above the ground." How the variation in 

 the vicinity of buildings can depend on the 

 wind was explained in 1861 by W. S. Jevons, 

 who said that a stream of air meeting an 

 obstacle leaps over it, flowing with increased 

 velocity above it, as a river flows fastest 

 through narrows. When two equal drops 



of rain fall into a current of air at points 

 where the velocity is not the same, one drop 

 will either approach toward or recede from 

 the other, and the quantity of rain falling 

 on the space beneath will be increased or 

 diminished. The large rainfall registered 

 at the Signal - Service station on Mount 

 Washington has recently been specially in- 

 vestigated. Four extra gauges, three inches 

 in diameter, were set up seventy-five feet 

 respectively north, east, south, and west 

 from the station-gauge. The observations 

 of thirteen months showed that precipita- 

 tion varies materially within one or two 

 hundred feet. It was found also that the 

 windward gauges generally recorded the 

 least rain, the central gauges more, and the 

 leeward gauges the most. Hence it is con- 

 cluded that the wind affects the distribution 

 of rain on the summit of Mount Washing- 

 tion in the same way as on the tops of 

 buildings. During this period the station- 

 gauge, which is eight inches in diameter, 

 was found to give larger readings than the 

 others, and a three-inch gauge was set up 

 near the large one for comparison under 

 the same conditions. The conclusion reached 

 was that the discrepancy was due to insuffi- 

 cient collection by the smaller gauge, and 

 varied as the square of the wind's velocity. 

 European observers have noticed no such 

 differences between the measurements of 

 three-inch gauges and larger sizes, but their 

 observations were made when the velocity 

 of the wind did not exceed twenty miles an 

 hour, while on Mount Washington it reached 

 seventy-five miles an hour. 



The Food of Animals. — The question 

 whether the distinction between herbivorous 

 and carnivorous animals is as clear as it has 

 been supposed to be is discussed in the 

 " Field Naturalist " and the " Journal of 

 Science." The prevailing theory is that the 

 primary animal life was herbivorous ; and 

 this must have been the case with the ear- 

 liest and lowest forms, which had nothing 

 but plants on which to feed ; but among 

 vertebrates, and especially among mamma- 

 lia, the earliest forms seem to have been 

 zoophagous or animal-eating. Among fishes, 

 amphibians, and reptiles, even in the earlier 

 geological epochs, the vegetable feeders are 

 found in a minority. The earliest fossil 



