333 



ANEMOMETER 



ANE'THUM GRAVEOLENS. 



334 



time occupied in passing a given station marked hourly, or at any 

 shorter interval that may be desired. 



The Rev. W. Foster, of Sturbington, near Portsmouth, has con- 

 trived an ingenious anemometer, which is fully described in Sir 

 W. Snow Harris's ' Report on the Working of Whewell's and Osier's 

 Anemometers at Plymouth during the years 1841,-42,-43,' presented to 

 the British Association for the Advancement of Science in 1844, to 

 which we are indebted for some of the preceding details. Foster's 

 anemometer consists of a cross horizontal fly three feet in diameter, 

 with four vanes each six inches square, and so contrived as to revolve 

 in one direction only. The revolution of this fly imparts motion to a 

 vertical shaft, at the lower end of which is an endless screw, which is 

 connected with a tram of wheels to a disc, twenty-two inches in dia- 

 meter, which is caused to revolve slowly in a horizontal plane, and 

 this disc thus registers the revolutions of the fly, which may be in any 

 convenient proportion to those of the disc. 



By means of a second vane and a vane-rod a second disc, nine inches 

 in diameter, is made to revolve. There is also a rain-receiver on the 

 roof, and a pipe by which the rain descends into a balanced gauge, the 

 reciprocating motion of which causes an axis to work in a toothed 

 wheel under the disc, through a space proportional to the quantity of 

 rain delivered at each tip of the gauge. There is also a rod set on 

 ii i' tinn-rollers, and furnished with a rack adapted to the tooth of a 

 horizontal rod projecting from the centre of a clock. There are 

 twenty-four teeth in the rack, so that the rod is moved hourly one 

 '!i\ i-4ou, by which motion three pencils are hourly moved upon the 

 respective discs, so that traces are obtained of the direction and 

 vcl'city of the wind, and of the nun for every hour. 



We give the following table as a specimen of the interesting results 

 operation of this instrument. It shows the total and mean 

 hourly velocity of each wind in miles. 



Professor John Phillips liad, in the Great Exhibition of 1851, an 

 anemometer for collieries, hospitals, &c., for ascertaining the velocity of 

 the current in the ventilation of such places. The pressure is received 

 "ii < semicircular disc of cardboard, suspended by the diameter and 

 measured on a graduated arc. By tables calculated from the equation, 



vi-1. -= M </ , the velocity is obtained in terms of the angle. 



M. de Hannault also exhibited a small travelling anemometer, consist- 

 in_r ,jf a series of fans which, by a simple contrivance, could be stopped 

 or set in motion almost momentarily. Its chief object was to deter- 

 mine the horizontal velocity of the air in a given time. 



In the anemometer erected at Kew Observatory Dr. Robinson's 

 method is adopted, namely, that of measuring the velocity of the 

 wind by the rotation of a system of hemispherical cups, the direction 

 being indicated by a dunble-whwl fan, like the directing vane at the 

 back of a windmill. A stout tubular support carries the whole of the 

 external part of the instalment, including the measurer of velocity, the 

 inn vane, and a rain gauge. All the rotatory parts of the anemo- 

 meter run upon friction-balls. The shaft of the apparatus for measur- 

 ing the movement of the wind by means of a diminishing tram of 

 wheels, is made to turn a cylinder upon which is wrapped a sheet of 

 paper of the kind used for metallic memorandum-books, which paper 

 receives a trace from a brass style. The sheet of paper is divided into 

 two sections, upon one of which is recorded the motion of the wind, 

 and upon the other the direction. As the cylinder is being turned by 

 the action of the wind, a clock carries a pencil along the cylinder at 

 the uniform rate of twelve inches in twenty-four hours. To the lower 

 end of the direction-shaft is attached a spiral of such a figure that 

 "1 t'> equal increments of radius; the edge of 

 * thin slip of brass, which touches the paper 



and records the direction of the wind on a rectilinear scale. When 

 the sheet of paper is taken off the cylinder after the lajise of twenty-four 

 hours, the motion of the wind and the direction are both found projected 

 in rectangular co-ordinates. This self-registering apparatus was designed 

 and constructed by Mr. R. Bcckley, assistant in the observatory. 



In a letter to the writer of this article Mr. Beckley remarks : " The 

 principal improvement I think, consists in the method of mounting, 

 by the application of the hollow shaft to the direction vanes ; as in 

 all cases where the cups have been used the velocity and direction of 

 the wind have been two distinct erections, whereas all that is necessary 

 in my case is a base to bolt the column upon. I also economise space 

 within the building. The method of registration consists in using 

 metallic paper, upon which brass becomes a pencil ; the form of 

 which is a very thin-threaded screw, whose pitch, in the case of the 

 velocity-pencil, is equal to a scale of fifty miles upon the paper. By this 

 means I get a very open scale in a small space. The pitch of the 

 direction-screw is equal to any openness of scale that is desirable. By 

 using this form of pencil I ovecrome the difficulty attending the old 

 method, namely, the pencil shifting off the scale, to obviate which, it 

 was usual to have three sets of scales upon the paper ; but even then, 

 should the wind go twice round in the same direction, it ceased to 

 indicate, whereas in my arrangement it must at all times register." 



With respect to anemometric observations at sea, Mr. Welsh, Direc- 

 tor of the Kew Observatory, gives the following method of making 

 allowance for the effect of the ship's motion upon the observed velocity 

 and direction of the wind : " By means of a portable Robinson's 

 anemometer, provided with a means of observing the total number of 

 turns made by the rotating part in any given time, observe the appa- 

 rent velocity of the wind, and record it in knots per hour. By an 

 anemoscope of any kind register the apparent direction of the wind. 

 From the log-book take the rate and direction of the ship's motion. 

 On a slate or other similar surface scratch a permanent compass circle : 

 set off from the centre of the circle, on the radius of the direction of 

 the ship's head, by any convenient scale, the number of knots per hour 

 the ship is going ; from this point draw a pencil line parallel to the 

 direction of the wind as observed by the anemoscope (that is, the 

 nt direction to which the wind is yuluy) ; set off on this line the 

 number of knots per hour as shown by the anemometer ; draw a line 

 from the centre of the circle to this last point. The length of this line 

 by the scale adopted, gives the true velocity of the wind, and its direc- 

 tion (carried back wards) shows the point from which the wind is com imj. 

 A parallel ruler divided on the edge is all that is required besides the 

 slate. It would be easy enough to contrive some mechanism to save 

 the trouble of drawing lines, but it would not, I believe, be any mil 

 simplification, and would increase the expense. The train of indi- 

 cating wheels might be so arranged that they at once indicate knots 

 per hour, without reference to tables, and can be readily set to zero for 

 a fresh observation." (' British Association Report,' 1856.) Professor 

 C. Piazzi Smyth, from a series of observations communicated to him 

 by Captain H. Toynbee, concluded that the only unexceptionable sta- 

 tion for anemometrical observations at sea was the mast-head. He 

 had therefore contrived an apparatus for measuring the direction and the 

 velocity of the wind, arranged with a view to such a position, and also 

 with a view to observe accurately the mean effects, and this by a 

 summation of every individual gust, even the lightest. For the most 

 accurate plan of securing data, he had arranged a method of electric 

 registration, which was carried on in the cabins below, while the 

 anemometers were measuring the wind aloft. ('British Association 

 I :. port,' 1855.) 



For the method of discussing the results obtained by means of 

 anemometers, see AKBO-DYNAMICS. 



ANEMONIC ACID. A name given to two distinct acids derived 

 from the Anemone Pultatilla, A. Pratensts, and A. Nemorosa. One of 

 these acids has the formula C^d u O u . The formula of the other is 

 doubtful. Neither acid possesses any especial interest. 



ANEMONIN (C^H^O,, ?). A white crystalline body found in the 

 water distilled from the Anemone Pulsutilla, A. Pratemis, and A. Nemo- 

 rota. It is poisonous, and slightly irritating to the skin. Alkalies 

 transform it into anemonic acid. 



ANE'MOSCOPE, an instrument for determining the directionof 

 the wind ; usually constructed by connecting with the spindle of a 

 weathercock the hand of a dial on which the points of the compass are 

 marked. [ANEMOMETER.] 



ANEROID BAROMETER. [BAROMETER.] 



ANE'THUM GRAVEOLENS (DILL) Medical Properties of. This 

 is an umbelliferous plant, native of the south of Europe, Astrakhan, 

 Egypt, and the Cape of Good Hope : it has either migrated or been 

 introduced into Egypt and the Cape. It is also cultivated in England. 

 It was in high repute among the ancients, both as a medicinal and a 

 savoury herb, being mentioned by Hippocrates and Dioscorides (Hvridov 

 of the latter) ; also in the Bible (Matt, xxiii. 23), where, however, it is 

 translated anise. The fruit is the part which is officinal. This consists 

 of a diacheuium formed of two flattened mericarps, on the back of 

 which is one, and on the commissure two vittx, containing the volatile 

 oil, on the presence and quantity of which the peculiar odour and 

 virtues of the fruit depend. The quantity of oil varies much according 

 to the degree of ripeness, the age, and, above all, the place of growth 

 of the fruit. Fruits too ripe, or very long kept, yield less than 

 gathered before perfect maturity, or very fresh ones. Those raised in 

 England are inferior to those from the south of Europe ; the clearer 

 and drier atmosphere of the latter favouring the elaboration of volatile 

 oils. To obtain it, the bruised fruit is submitted to distillation with 

 water : 2 cwt. of good fruits yield 8 Ibs. 5 oz. of oil. (Pereira.) The 



