443 
THE APRIL MEETING^ 1844 . 
ferently colored cloths in the enow, and showing’ the depth to which they sunk, 
are still quoted, and great praise has been bestowed abroad on a more elaborate 
series of experiments, by a descendant of his, Dr. A. D. Bachc, proving that this 
law does not hold good as to heat, unaccompanied by light. The experiments of 
Saxton and Goddard demonstrate that solid bodies do slowly evaporate. It is 
proper here to mention our countryman, Count Rumford, whose discoveries as to 
the nature and properties of heat, improvement in stoves and gunnery, and in 
the structure of chimneys and economy of fuel, have been so great and useful. 
Light accompanies heat of a certain temperature. That it acts directly to in¬ 
crease or decrease magnetic force, is not yet proved; and the interesting exper¬ 
iments made by Dr. Draper, in Virginia, go to show that is without magnetic in¬ 
fluence. The discussion of this subject forms the branch of optics, touching phy¬ 
sical science on one side, the most refined, and the highest range of mathematics 
on the other. Rittenhouse first suggested the true explanation of the experiment, 
of the apparent conversion of a cameo into an intaglio, when viewed through a 
compound microscope, and anticipated many years Brewster’s theory. Hopkinson 
wrote well on the experiment made by looking at a street lamp through a slight 
texture of silk. Joscelyn, of New York, investigated the causes of the irradiation 
manifested by luminous bodies, as for instance the stars. Of late, photographic ex¬ 
periments have occupied much attention, and Draper has advanced the bold idea, 
supported by experiment, that the agent in the so called photography, is not light, 
nor heat, but an agent differing from any other known principle. Henry has in¬ 
vestigated the luminous emanation from lime, calcined with sulphur, and certain 
other substances, and finds that it differs much from light in some of its qualities. 
Astronomy is the most ancient and highest branch of physics. One of our earliest 
and greatest efforts in this branch was the invention of the mariners’ quadrant, by 
Godfrey, a glazier of Philadelphia. The transit of Venus, in the last century, cal¬ 
led forth the researches of Rittenhouse, Owen, Biddle, and President Smith, 
near Philadelphia, and of Winthrop, at Boston. Two orreries were made by Rit¬ 
tenhouse, as also a machine for predicting eclipses. Most useful observations, con¬ 
nected with the solar eclipses, from 1832 to 1840, have been made by Paine, of 
Boston. We have now well supplied observatories at West Point, Washington, 
Cambridge, Philadelphia, Hudson, Ohio, and Tuskaloosa, Alabama, and the valuable 
labors of Loomis, Bartlett, Gilliss, Bond, Pierce, Walker, and Kendal, are well 
known. Mr. Adams, so distinguished in this branch and that of weights and mea¬ 
sures, laid last year the corner-stone of an observatory at Cincinnati, where will 
soon be one of the largest and most powerful telescopes in the world. Most inter¬ 
esting observations as to the great comet of 1843 were made by Alexander, An¬ 
derson, Bartlett, Kendal, Pierce, Walker, Downes, and Loomis, and valuable as¬ 
tronomical instruments have been constructed by Amasa Holcomb, of Massachu¬ 
setts, and Wra. J. Young, of Philadelphia. 
It is difficult to class the brilliant meteors of November the 13th, 1833. If such 
meteors are periodic, the discovery was made by Professor Olmsted ; and Mr. Her¬ 
rick, of New Haven, has added valuable suggestions. The idea that observers, dif¬ 
ferently placed, of the time of appearance and disappearance of the same meteor, 
would give the means of determining differences of longitude, was first applied in 
our own country, where the difference of longitude of Princeton and Philadelphia 
was determined by observations of Henry and Alexander, Espy and Bache. In 
meteorology our countrymen have succeeded well. Dr. Wells, of South Carolina, 
