282 METEOEOLOGICAL EEPOKT, 1808, 



or any other medium which has the property of rapidly absorb- 

 ing Vv^atery vapour. By these simple means an artificial locality 

 may be produced, and invalids, whose circumstances or avoca- 

 tions prevent them from seeking a climate suited to their peculiar 

 constitution, may to a great extent, by the aid of this instrument, 

 obviate the necessity of doing so." 



The instrument in use should be placed in a part of the room 

 away from the fire and not exposed to a draught. A recess in 

 the same side of the room as the fire is generally the best place. 

 A difference of from 6° to 8° between the readings of the two 

 thermometers will generally be found to give a pleasant degree 

 of humidity. To gardeners, especially those who have the care 

 of vineries and stoves, the hygrometer is of the greatest use and 

 importance. Every one at all conversant with such matters 

 knows that in " Greenhouses plants become shrivelled or other- 

 wise injured before there is any suspicion of an alteration in the 

 humidity of the air ; and when suspected a quantity of water, 

 without any guide as to the amount required, is thrown on the 

 plants and walls A dry and wet bulb thermometer, pro- 

 perly used, and its indications attended to, may be made the 

 means of preserving many valuable plants which might otherwise 

 perish in an ill-regulated atmosphere. 



" To make the uastrument properly available for this purpose, 

 a knowledge is required of the climatic conditions of the coun- 

 tries in which the plants naturally have their growth. For ex- 

 ample, suppose the temperature of the climate to be 70°, and its 

 mean state of humidity about sixty or seventy per cent, of the 

 quantity of aqueous vapour which the air would contain if satu- 

 rated, it is necessary then that the reading of the dry thermo- 

 memeter should be maintained at 70°, and the reading of the 

 wet between 60° and 64°. These last numbers are found by 

 looking in the table at division 70° of the dry bulb, and under 

 degree of humidity for 60° or 70°, which gives corresponding 

 ranges between 60° and 65°." 



It is to be regretted that many persons, who do not hesitate 

 to spend large sums of money on their gardens, yet often refuse 

 to spend a trifling sum in comparison on the purchase of a few 



