192 Ohituary. 



same colour as the spirit of wine in the other, and is kept constantly moist 

 by some capillary substance connecting it with a vessel or phial holding 

 water. The caloric thus abstracted from the liquid in the moistened ball 

 by evaporation on its surface, depresses the temperature in proportion to 

 the intensity of evaporation or capacity of the air for holding moisture in a 

 state of vapour. The difference of temperature indicated by the thermo- 

 meter with the moist ball forms only one co-efficient, along with the actual 

 temperature of the air, force of vapour, and atmospherical pressure, in 

 the calculation, to find the quantity of moisture in a cubic foot of air, the 

 dew point, or, as some call it, the " point of deposition," &c. If Mr. Main 

 wishes further information on this point, I must refer him to Brewster's 

 Encyclopcsdia (article Hygrometry, by, I believe. Dr. Anderson of Perth), 

 and to Professor Leslie's articles of the same nature in the Encyclopcedia 

 Bntannicay in which he will find the instrument fully described \x)^ its origiiial 

 form, where the balls are filled only with air. He will also find the tables 

 and formulae necessary to ascertain the quantity of moisture in a given 

 volume of air, point of deposition, &c. He will observe from what I have 

 stated that the " dew point " is " a point in nature." He asks " which 

 degree of increasing moisture on a body cooled down by artificial evapo- 

 ration can be properly called the dew point ? " which he says " begins at the 

 second degree below the temperature of the air (whether visible or not.)" 

 In reply, I would say that the point at which moisture becomes visible in 

 the cooled substance is the point of temperature generally, and I think very 

 properly, called in practice the " dew point." It may be possible, as he 

 says, that " a solid body begins to be moistened at the second degree below 

 the temperature of the air, whether visible or not;" but if " invisible " how 

 is he to know it ? for, in certain states of the atmosphere, we find that 

 such moisture does not become visible at the second, at the fifteenth, or 

 even at the twentieth degree below the temperature of the air with the best 

 microscopes. Mr. Main is too much a lover of science not to excuse 

 the freedom of these remarks, which my limits, in the mean time, prevent 

 me from extending. Yours, &c. — A. Goriie. Annat Gardens y Dec, 1. 1830. 

 Comparative Indications of Spring. — Would it not be of some use for one 

 of your correspondents in every county of Britain and Ireland to send you 

 a notice, in the last week of every February, on what day of that month 

 the common snowdrop, the striped or Scotch crocus (C. biflorus), the 

 aconite, the white Christmas rose, and the catkins of the hazel, came into 

 flower ? The plants must have stood undisturbed in the same spot for two 

 years, otherwise their indication will not be accurate. — J, Lequin. Feb, 5, 

 1831. 



Art. X. Ohituary, 



JDlEDy on the 26th of December, aged 59, at his house at Tottenham, 

 Thomas Carpenter, Esq., an eminent naturalist and cultivator of science. 

 His researches and discoveries in the economy and instinctive operations of 

 insects and microscopic animalcula were original, extensive, and curious. 

 Many of the latter were but the ten-millionth part of an inch, yet all in 

 life or animated motion. He improved the method of illuminating the 

 minutest opaque objects by candle-light under the compound microscope. 

 He published many of his observations and discoveries in the latter 

 volumes of GiWs Technological and Microscoj)ical Monthly Repository , and 

 it may be considered a loss to science that he did not live to continue these 

 observations. — Anon. J«w. 1831. 



