141 



! 1 



i \ 



loom or on the spindle, such an instrument offers a 

 ready means for determining the actual state and 

 remedying the defects of diminished atmospheric 

 moisture. 



HYGROMETERS. 



Hygrometric instruments of various kinds have 

 been devised, but have all proved unsatisfactory- in 

 practice, except that known as August's Psychrom- 

 eter or, as it is commonly termed, "the Wet and Dry 

 Bulb Thermometer," sometimes simply the " Wet 

 Bulb Thermometer." This consists ot two delicate 

 thermometers placed near each other, the bulb of 

 one being covered with very thin muslin, kept moist 

 by water supplied from a vessel beneath, through ca- 

 pillary attraction. The dryer the air, or the farther it 

 is from saturation, the more rapid will be the evap- 

 oration from a wet surface; and, as evaporation ab- 

 sorbs heat, the more rapid the evaporation the 

 greater will be the consequent cooling of the body 

 from which the evaporation proceeds. As, in this 

 case, this is the thermometer whose bulb is wrapped 

 with the wet muslin, this reduction of temperature 

 is indicated by the lower degree reached by the 

 mercury in its tube. This lower degree is the tem- 

 perature of evaporation at the time of observation. 

 If the air be very nearly sc*turated with moisture, 

 the difference between the "wet and dry bulbs" will 

 be very small ; but the proportional quantity of hu- 

 midity present cannot be directly determined by ob- 

 serving this difference. The proportional quantity 

 of moisture present, or the relative-humidity, must 

 be found by consulting elaborate and extensive 

 tables, which have been prepared for practical me- 

 teorologists, and derived from experiments on the 

 elastic force of aqueous vapor at different tempera- 

 tures. To render it unnecessary to use such tables, 

 while we attain a sufficiently accurate expression of 

 the humidity present, and that more easily and 

 promptly, " Lippincott's Vapor Index " has been 

 constructed. (For the mode of using the "Index," 

 together with directions for determining the number 

 of grains of vapor in a cubic foot of air, directions 

 for obtaining an approximate "Dew Point," and 

 sundry recommendations from eminent meteorolo- 

 gists, see the "Index" and accompanying text.) 



Having determined, by observations of the Psy- 

 chrometer and the "Vapor Index," the state of tjie 

 air of an apartment, as respects humidity, — if this 

 prove deficient in quantity or proportion, a further 

 supply should be found in evaporation from wide 

 pans, kept filled with water by a self-acting cock, — 

 or vapor may be supplied by means of an iron tube 

 inserted through the furnace in the midst of the 

 burning coal, and connected with a reservoir of 



fV -^wri ■ — ^ — — . — ™™™___«_„ — , ■ — 



water, the outer extremity of the tube opening, of 

 course, into the room to be benefited by the arrange- 

 ment. 



The common practice of placing a small vessel of 

 water upon a stove or fumace, is a' together inade- 

 quate to produce any valuable modification of tne 

 humidity of the air of an apartment. It has been 

 shown that dry air is favorable to the radiation of 

 heat, while moist air is an absorbent, or checks this 

 loss of heat. Dry air, also, induces excessive insen- 

 sible perspiration, while moist air acts as a regula- 

 tor or restrainer of this excess. As both radiation 

 and perspiration are cooling processes, which pro- 

 ceed more rapidly in dry air than in a moist atmos- 

 phere, our bodies must lose more heat, and become 

 sensibly cooled more readily in the former than in 

 the latter. A higher degree of humidity in a warmed 

 apartment is, therefore, favorable to the feeling of 

 comfort; while dryness may suggest chilliness, even 

 at the same temperature. More heated air, therefore, 

 thrown into the apartment, the relative dryness is 

 augmented, the skin, lungs, &c. , are subjected to a 

 greater parching influence, — the innermost recesses 

 of tiie body are affected thereby, and the whole 

 circle of organic processes is disturbed, and the sys- 

 tem too often prepared for the advent of diseases 

 which sap the strength and may, finally, destroy the 

 habitual inmates of rooms heated by the favorite 

 furnace, when no attention is paid to the conditions 

 of humidity present. 



Note. — "The evaporation of water from the body 

 is intimately connected with health." "The func- 

 tions of the skin are interrupted, and affections of 

 the throat, bronchitis, pulmonary consumption, peri- 

 carditis, inflammation of the stomach, and dyspep- 

 sia, rheumatism, gout, &c , are among the diseases 

 which eventually manifest themselves." "Due reg- 

 ulation of the humidity of the air of an apartment 

 is as important to the health of its inmates, as its 

 freedom from poisonous or deleterious gases." — 

 Dr. C. M. Wetherell, in Report on Warming 

 and Ventilating the Capitol at Washington, May, 

 1866. 



As comfort may be obtained at a lower tempera- 

 ture, in rooms in which the air abounds in moisture, 

 while the heat from furnace is also more readily and 

 largely conveyed to all parts of the room, the con- 

 sumption of fuel may be proportionally lessened. — 

 In a moist atmosphere, a temperature from 5° to 8° 

 lower will be found as agreeable as that generally 

 found to prevail in living rooms as usually heated, 

 while a marked relief from the sense of oppression 

 known in dry apartments will be experienced. The 

 Psychrometer or Wet Bulb Thermometer, with the 



— J 1 



