14 



SCIENCE. 



[Vol. VIII., No 178 



tail of this species the appearance of feeling about 

 for something, on its own account. The curves are 

 so irregular at times, that the organ appears as if 

 broken in several places. "When at rest, some indi- 

 viduals have the habit of curling the tail closely 

 against the body in a flat coil. Its capabilities are 

 best seen in slender specimens, in which the tail is 

 less thick and clumsy. Very likely Amblystoma 

 jefEersonianum, and species of similar build, have 

 the organ similar in sensitiveness and utility. Am- 

 blystoma mavortium, however, is lower in rank, and 

 has the tail better adapted for swimming or pushing, 

 as in other more aquatic forms. S. Garman. 



Cambridge, Mass., June 27. 



Association of official agricultural chemists. 



The next meeting of this association will begin 

 Thursday, Aug. 26, in the library of the Department 

 of agriculture. All agricultural chemists holding 

 official positions under the national or state govern- 

 ments, in agricultural colleges or experiment-stations, 

 are entitled to membership. All other chemists in- 

 terested in any way in the analysis of fertilizers or 

 food-products are invited to attend the meeting, to 

 present papers and take part in the discussion. 



One of the chief objects of the association is to 

 secure uniformity in methods of analysis employed. 

 The attainment of such uniformity is of little less 

 value than accuracy, in work of this kind. 



I take this method of calUng the attention of the 

 ■chemists of the country, who are not members of 

 the association, to the coming meeting. 

 H. W. Wiley, 

 Pres., and chairman of exec. com. 

 Washington, June 86. 



Barometer exposure. 



I have read with pleasure the paper referred to by 

 Mr. Gilbert in his letter {Science, vol. vii. p. 571). 

 His method seems to have shown, as clearly as could 

 be without direct experiment, that the wind had the 

 effect of lowering the barometer-readings in the 

 l)uilding on Mount Washington. This direct evi- 

 dence, if needed, has, I think, been supplied by the 

 observations on Blue Hill, where it has been noticed, 

 not only that the barometer in the building suddenly 

 falls if the wind-velocity suddenly increases, but 

 that during high winds the pressure in the building 

 can be varied at will by merely opening and closing 

 an aperture in the top of the building. 



It does not seem unsafe, then, to draw one or two 

 conclusions from these facts. In Loomis's tenth 

 paper (Amer. journ. sc, January, 1879), from an 

 examination of a large number of storms, he arrives 

 at the remarkable conclusion that "the low centre 

 at the height of Mount Washington sometimes lags 

 behind the low centre at the surface of the earth, 

 apparently as much as two hundred miles." Mount 

 Washington is only about one mile high ; and if we 

 draw two lines, — one to i-epresent the earth's sur- 

 face, and the other the storm-axis, — and make them 

 diverge only one division in two hundred in length, 

 the two lines will appear to the eye almost parallel. 

 Such an inclination of the storm-axis seems incredi- 

 ble, and renders it probable that the apparent lag- 

 ging was due to some other cause. Loomis shows, 

 in this same paper, that the occurrence of high winds 



on Mount Washington from any easterly quarter is 

 exceedingly rare ; and in his eleventh paper he says, 

 "In a majority of those cases in which an area of 

 low barometer passes ever New England, attended 

 by the usual system of circulating winds at the sur- 

 face stations, this system of circulating winds does 

 not extend to the height of six thousand feet." The 

 effect of the indraught below only makes itself felt 

 at the height of Mount Washington in front of 

 storms by lessening the velocity of the prevailing 

 westerly current, and in the rear of storms by in- 

 creasing the velocity of this current. 



This at once suggests that the apparent lagging of 

 the storm-axis, or rather of the time of minimum 

 pressure, on Mount Washington, is due to a mechani- 

 cal effect of the wind on the observatory. 



Mr. Gilbert has shown in his paper (pp. 531-533), 

 from a series of observations, that wind-velocities 

 of forty miles per hour from the north-west had the 

 effect of lowering the pressure in the observatory on 

 Mount Washington as much as eight-hundredths of 

 an inch ; wind-velocities of fifty miles, as much as 

 thirteen-hundredths of an inch ; and he estimated 

 that wind- velocities of one hundred miles would 

 lower it as much as half an inch. This equals any of 

 the effects found by Loomis, and gives a plausible 

 reason why the minimum pressure should occur later 

 on Mount Washington than at sea-level. The same 

 explanation applies to the lagging of the times of max- 

 imum pressure, since Loomis has shown in his second 

 paper (Amer. journ. sc, January, 1875) that the 

 wind-velocities are larger in front than in the rear 

 of maximum pressures. 



Loomis also found that there was a lagging of the 

 diurnal curves of pressure on Mount Washington 

 and other mountains. He says in his tenth paper, 

 " At the base of Mount Washington the principal 

 maximum occurs at 8.30 a.m., but on the summit it 

 does not occur until noon, being a retardation of 

 three hours and a half." 



Mr. Gilbert shows, on p. 526 of his paper, that 

 from June 26 to June 28, 1873, some element on 

 Mount Washington, v/hich was undoubtedly the 

 pressure, went through a diurnal variation coinci- 

 dent with the wind- velocity. During this time the 

 wind each day reached a maximum near midnight, 

 and a minimum near noon. This is a normal feature 

 on high mountains ; and if an increased wind- 

 velocity tends, by a mechanical action on the build- 

 ing, to make the barometer read lower, it is readily 

 seen that the pressure would tend to be lowest near 

 midnight, and highest near mid-day. If, now, a 

 double diurnal oscillation due to other causes be 

 superposed on this, the chief maximum would occur 

 much nearer noon than at lower stations, where the 

 action of the wind is in the opposite direction. 



The variations in the wind's velocity may not be 

 the only cause of the phenomena considered in this 

 letter. Loomis thinks that the wind-directions, and 

 Ley that the upper cloud-motions, indicate a lagging 

 of the storm-axis ; and it seems probable that the 

 expanding and contracting of the air from heat and 

 cold have something to do with the occurrence of 

 the chief maximum on mountains near noon, and in 

 the lagging of the minimum pressure in storms ; but 

 the variations in the wind- velocity are undoubtedly 

 an important factor, and it is very desirable that its 

 influence might be eliminated. 



H. Helm Clayton. 



Blue Hill meteor, observ., June 28. 



