Page:Popular Science Monthly Volume 45.djvu/735

Rh of experts, to be only a confession of weakness rather than a disposition earnestly to consider the whole question with a view to the radical remedy of the evils. The human nature of the judge is recognized and provided against. . . . The jury is selected so as to be free from bias, and is protected as well. Other witnesses are not expected to take the part the scientific expert is almost compelled to take. In fact, if deliberately planned, there could hardly be a network of conditions devised calculated to produce so many of the evils of scientific expert testimony complained of or to cloud this testimony of highest intrinsic value, having the highest degree of certainty, and in a field altogether its own." These witnesses are sometimes supposed to be selected on account of their ability to express a favorable opinion, when they are flippantly styled "adroit advocates of the theory of the party calling them"; but in how many cases. Prof. Himes asks, "does favorable opinion—or bias, if you please—precede the call of an expert rather than depend upon the call?" And the still more pertinent question, "How many experts are not in the particular case because their opinions are not wanted by the party who consulted them?"

Death Valley, California.—The principal features of popular interest in Death Valley, California, as described in Prof. Harrington's Notes on its Climate and Meteorology, are its excessive heat and dryness. The temperature rises occasionally in the shade to 122º, rarely falls at any time in the hot months below 70º, and averages 94º. It is not only hot in the summer, but consistently hot, and the heat is increased by occasional hot blasts from the desert to the south. The air is not stagnant, but in unusually active motion. Gales of a few hours' duration are very common, and sometimes produce sand whirls and sand storms. Rains may fall frequently in the mountains and occasionally in the valley. Clouds are by no means lacking, and water can probably always be found in the soil at the depth of a few feet, yet the heat and wind together keep the surface very dry and the relative humidity low. Animal and plant forms are comparatively few, and the former are usually nocturnal to avoid the heat. Both heat and aridity are increased by the character of the valley. It is narrow and deep, apparently the bed of an old sea, inclosed by high and dry mountains. The white and shifting sands become much heated under the noonday sun; the rest of the surface is in part salt and alkali, in part probably wash from the mountains, and in part a loose, spongy earth, over which it is difficult to move. With the exception of a few springs, the water is bitter and unwholesome. The meteorological features of interest lie, for the most part, in those modifications of diurnal changes which are due to the topography. The range of temperature is unusually great. The hourly progress of the wind shows enormous changes in speed, in direction, and in temperature. The diurnal change in the barometer is the most characteristic of the form found in continental valleys. It is of the purest single maximum type and has the largest amplitude known. With these features go sharp thunderstorms, limited to certain hours of the day, and daily gales and hot blasts. It is also noteworthy that the absolute humidity here is fairly constant, and is that belonging to that part of the world. The air in the valley is part of the general aëerial ocean, and this shows no sharp contrasts in its moisture contents, except when wind prevails across a mountain ridge. Here the prevailing winds are up and down the valley, and its relative aridity is due to its higher temperature. The winter climate is believed to be cool and salubrious, with an inch or two of rain.

The Vacuum Jacket and Liquid Oxygen.—Prof. Dewar protects his liquefied gases, in order to keep them in that state, from the heat of convection, by inclosing them in a vacuum jacket; and from the heat of radiation by silvering the surface of the containing vessel. He is thus able to keep liquid air for thirty or forty hours. The vacuum used contains a little mercury vapor, which, though present in very minute quantities, can be condensed into a bright mirror by cooling the outside surface of the vessel with liquid air. Among the experiments made in one of Prof. Dewar's lectures to illustrate the properties of liquid oxygen, alcohol, which freezes at $$-$$120º, solidified when dropped into it, and in that state would not take fire.