

METEOROLOGY. 



[INSTRUMENTS. 



balanced and hung on gimbals, having vortical fan* to 

 carry it in the direction of tin- wind, mid horizontal fans 

 it to tip tip or Joiru, to show the angle at which 

 ir i< Mowing. 



The Jiain Ainjle in a simple contrivance for showing 

 the angle at which the rain descend*. It consists of a 

 move* ulung a graduated arc. 



The Distant* Measurer. A modification of the car- 

 I nt.-i'.-. nil.-, having an elevated eye-hole, fixed vertically 

 in tlif jint, and a sHOdsT ]>i" screwed vertically on each 

 leg of the rule. The rule itself slides on a graduated arc. 

 In ordi r to measure approximately the distance of a 

 peculiar cloud, or other celestial phenomenon, from any 

 fixed ol-jivt, tho log* of the rule aru opened until one of 

 the i. -inc.il ]>ins covers the object to be measured, and 

 the other the object to which it is referred. The distance 

 will bo seen on the graduated are. 



Ozonometcr. A MBMsj contrivance for ascertaining 

 thf amount of ozone in the atmosphere. Ozone was 

 discovered by Dr. Schoubein of the University of Bale, 

 in tho year 1848. Test-papers are hung in a situation 

 where there is a free current of air, but not in sunshine ; 

 the north face of a thermometer-stand is a convenient 

 situation. These papers will remain colourless if thero 

 be no ozone present, and will be more or less tinged with 

 hliic, as the ozone is more or less powerful. A scale of 

 different tints, marked froinO to 10, is furnished with the 

 test-papers, to which the slips are referred after exposure 

 to the atmosphere, immediately after immersion in 

 water for the space of one minute. 



These test-papers are made in the following manner : 

 200 parts of distilled water, 

 10 ,, of starch, 



1 ,, of iodide of potassium, 



boiled together for a few seconds, and then slips of 

 bibulous paper dipped into the solution ; when dry, they 

 are leady for use. If there be any ozone present in the 

 air, it seizes on the potassium the blue colour left being 

 i'xliile of starch. Other test-papers have been prepared 

 by Dr. Moffat of Hawarden, which do not require to be 

 plunged into water, in order to bring out the proper 

 colour. Dr. Moffat's test-papers must be kept in tho 

 dark. They are placed in a box, the bottom of which 

 is perforated with holes for the free passage of air. 

 These test-papers, if kept in the dark, will last for 

 several years, retaining the amount of discoloration. 



The Wind-Vane should be so contrived as to move 

 with the least amount of friction ; otherwise, in calm 

 weather, the changes will not be seen to take place in the 

 direction of the wind at the proper time. 



The A tmotpheric Recorder, although too expensive for 

 tho ordinary meteorologist, still cannot be passed over iu 

 Kili-nce. Having had one in work for a year, we can speak 

 of its value. Every change in the atmosphere is written 

 , by pencils at the precise moment of occurrence. 

 It is merely requisite to supply the cylinders with suf- 

 ficient paper ; after which, if the clock be occasionally 

 wound up, and the pencils kept capable of drawing 

 a clearly-defined Hue, no further care or trouble is 

 needed. This machine is incessantly writing down the 

 force of every gust of wind, the extent of every change 

 in its direction, the commencement and termination of 

 every shower, the quantity of rain which has fallen, and 

 the amount of evaporation and electricity. The 

 .re of the air, tin- pressure and hygrometrical 

 condition, are recorded every quarter of an hour. The 

 discussion of these records cannot fail in being productive 

 of much good to meteorologist*. Mr. Dolloud makes 



this ln.-i- !i I r.f. 



The Aciinometer. An instrument for ascertaining the 

 force of solar radiation. It consist* of a large hollow 

 cylinder of glass, soldered at one end to a thermometer 

 tube, terminated at the other end by a ball drawn out to 

 a point, and broken off so as to leave the end open. The 

 cylinder is closed at the other end. It is filled with a 

 deep blue liquid (amuionio sulphate of copper). The 

 cylinder is enclosed in a chamber, which is blackened on 

 three sides. Thin instrument requires careful manipula- 

 tion, and i* but little used. 



Ivientity of Light. The gauge for ascertaining this 

 consists of a long narrow box, with a window at on. . n.l 

 facing the north . The box is ; ..int.-il Mark inside, ith 

 a white belt of a couple of inches in width, graduated 

 up to 100. The brighter the day, tho further can the 

 figures be seen up tin 



Th Transit Instrument is a useful addition. It lias 

 been well described by Mr. Breen in the Section on 

 Astronomy. A very close approximation to correct time 

 may be obtained by the use of Dollond's Portable Transit. 

 Agoodastronoimr.il clock, witli a mercurial pendulum, 

 ought to be found in every observatory, and a 

 watch in tho i . k. t of every observer; each should be 

 provided with tho seconds-hand. 



Jf'A. . ,'j, 1,7, r, invented by tho Rev. Dr. 



\Vhewell, is an ingenious .self- registering anemom 

 which gives the amount of horizontal movement in the 

 air. A system of wheels is worked by windmill-sails, 

 according to the velocity of the wind ; and these carry a 

 pencil, which is constantly recording the direction and 

 velocity of the wind. 



Osier's Anemometer constantly records the force and 

 direction of the wind, and also the amount of rain. An 

 admirable invention. Unfortunately, such instruments 

 as this and Dr. Whewell's are too expensive for the 

 majority of meteorological observers. 



The JSlectrical Observatory at Kew, under the able 

 management of Mr. Ronalds, has become a most im- 

 portant meteorological station, being, in fact, a collection 

 of all requisite electrometers ; a brief description of 

 which will be found in Dr. Drew's Practical Meteor" 



DanieWt Hygrometer. An instrument for ascertaining, 

 from direct observation, the temperature of the dew- 

 point. This is an interesting contrivance, as a rii 

 dew is precipitated at the temperature of the dew-point. 

 It consists of two glass balls, communicating with each 

 other by means of a bent tube. The one ball is of black 

 glass, and the other transparent. A thermometer is 

 fixed with its bulb within the blackened ball ; and as 

 soon as three-fourths pf this ball is filled with sulphuric 

 ether, it is immersed. The air having been exhuu 

 the tube is hermetically sealed. The transparent ball is 

 covered with muslin. A duplicate thermometer for 

 ascertaining the temperature of the air, is attached to 

 the stem of the instrument. To find tho temperature of 

 the dew-point, all the ether must bo made to run into 

 the black ball ; ether is then poured from a phial on tho 

 muslin : this produces rapid evaporation, and the tem- 

 perature is cooled down to that of tho dew-point ; at 

 this temperature, a ring of dew is formed round the 

 black bulb, and at this instant the immersed thermometer 

 must be read off ; rapidity of observation being neces- 

 sary, as the temperature will continue to fall below this 

 point, and the ring of dew also to increase in width. In 

 a few seconds the ring will gradually disappear, and at 

 this moment the thermometer should bo read a second 

 time. The mean of the two readings will give the > 

 pn-.ituro of tho dew-point It is necessary that the 

 ether should be very good. 



Tho results obtained by actual observation and by calcu- 

 lation (from tho wet and dry-bull > thermometers) are very 

 nearly identical, as tho following illustration will show : 



By Obserriititin. 

 Daniell's hygronvtcr, temperature of air . . SCO" 

 Daniull's hygrometer, temperature of dew-point 



when ring was formed ..... 48'1 

 Daniell's hygrometer, temperature of dew-point 



when ring disappeared . . . . . 48 "2 

 Daniell's hygrometer, mean temperature of dew- 



point 481 



Daniell's hygrometer, temperature of dew-point 



bulow temperature of air . . . .7 '> 



By Cakulati'iii. 



Temperature of dry bulb 56 '0 



Temperature of wot bulb ..... C-'O 



Calculated dew-point 48'2 



Temperature of dew-point below temperature of 



air 7'8 



