274 



Tlic Country Gentleman's Magazine 



capable of supporting a column of about 33 

 feet of water. 



The tube must always be kept half filled 

 with water — viz., exactly to the zero mark, 

 from which the upward and downward scales 

 begin. For easier observation, the water may 

 be coloured with cochineal, or with decoction 

 of logwood, to which a few grains of alum 

 have been added. In great degrees of cold 

 a saturated solution of sea-salt may be 

 used instead of water, the specific gravity 

 of which is 1.244. If the force in the fol- 

 lowing table for any height be multiplied 

 by the specific gravity, the product will 

 be the true force, has measured by the solu- 

 tion. 



The table exhibits the force of the wind 

 on a square foot, in pounds weight, for different 

 heights in the column of water in Lind's 

 Anemometer : — 



0-50 

 0-25 



0-05 

 o-oo 



Designation of Wind. 



Hurricane . . . 

 Violent Tempest . 

 Tempest . . . . 

 Storm . . . . 

 Very High Winds. 

 High Wind . . . 

 Strong Breeze . . 

 Fresh Breeze . . 

 Breeze . . . , 

 Pleasant Wind . 

 Calm 



Pressure in lbs. 



3175 



26-04 



20-83 



15-62 



10-42 



5-21 



2 -60 



1-30 



0-52 



0-26 



0-00 



The air depresses the water in the limb 

 which is in connexion with the open horizon- 

 tal mouth d opposed to the wind, and raises it 

 in an equal degree to the other limb c (fig. 2). 

 Hence, to measure the force of the wind by 

 this instrimient, the amount of depression in 

 the one limb should be added to the amount 

 of elevation in the other. To save this 

 trouble, however, and ensure accuracy, the 

 same end is attained by reckoning each half 

 inch as a whole inch, and dividing it into 

 tenths. The scale is therefore so divided. 

 By looking at either limb the reading is at 

 once taken accurately by reading off the 

 scales as inches and tenths of inches. The 

 instrument, when used, may be carried in the 

 hand to a favourable position on the ground 



for receiving the full force of the breeze, far 

 above the interference of buildings or trees ; 

 and being placed there and screwed into a 

 firm support, about four feet above the ground, 

 the readings are easily taken. The disc 

 through which the pivot p passes, is divided 

 like a compass card, so that by setting the 

 instrument with the north and south points of 

 the card in the direction of the true meridian, 

 the direction, as well as the force of the wind, 

 will be indicated. 



There are several other Anemometers, but 

 of complex and expensive character, suitable 

 only for meteorological observatories. Osier's 

 and Dr Whewell's are the best. Drew's 

 Practical Meteorology is a^ very simple and 

 practical book, and affords full information on 

 the use of the Anemometer as well as all 

 other meteorological instruments. 



APHIS BRUSH.— See page 123. 



ASPARAGUS KNIFE.— It is not the prac- 

 tice of gardeners to use an implement of this 

 description for cutting the shoots of asparagus. 

 A commom pruning knife is thought to 

 answer equally well ; but the late Mr MTn- 

 tosh, in his excellent Book of the Garden, con- 

 demns this practice ; for the cleanness of a 

 wound with a sharp knife leaves the vessels 

 open, and a considerable waste of sap is the 

 result. Fig. 3 shews the form of knife re- 

 commended by Mr MTntosh. It has a thin 

 blade about nine inches long, with a wooden 

 handle, and is slightly hooked at the point, 

 which renders it less liable to cut the under- 

 ground buds, while the serratures on the con- 

 cave side more readily catch the shoot 

 intended to be cut. Fig. 4 represents an- 

 other form of knife. The following remarks 

 as to the use of this implement, from the same 

 authority, may be useful : — " Remove Avith 

 the side of the Asparagus Knife a little of 

 the soil from around the base of the buds ; 

 push the knife gently downwards, keeping 

 it quite parallel and close to the shoot to 

 be cut, taking great care in doing so that 

 none of the buds yet underground are cut 

 or injured. When the knife is as deep as 

 the base of the shoot, give it a sligh 



