350 ' Miscellanies. 



ers of the parts of the earth, follows certain laws of increase and de- 

 crease ; and the entire quantity of each year descends to a certain 

 depth, where it is succeeded by the quantity thrown upon the earth 

 in the preceding year, which has not yet been dissipated ; below 

 that, lies the stratum occupied by the solar heat of the preceding 

 year, and so on, until at length, at a certain depth, this solar heat 

 ceases to be perceptible. He shewed that the mean annual quanti- 

 ty of this solar heat, was such as would melt fourteen metres, or 

 about forty five feet of ice, encircling the entire surface of the earth. 

 He next considered the central heat of the earth, and the experi- 

 ments and observations by which its existence was placed beyond 

 doubt, and the law of its distribution, as it ascended to the surface, 

 traced ; and he stated that the issue from the surface at each part 

 was so much in a century, as could be capable of melting three me- 

 tres or about ten feet of ice heated upon that surface. He then 

 discussed the subject of Cosmical heat — shewing the probability that 

 the regions of space were not of a uniform temperature ; and hence 

 he concluded that all the bodies of the solar system had a tendency 

 to acquire the temperature of that part of space in which they are 

 placed ; and that the heat of the planetary spaces, was only about 

 50° below the freezing point. 



Sound. — Prof. Reid stated, that when the English fleet was en- 

 gaged in the blockade of Copenhagen, being in a very extended 

 line, ships at the one end distinctly heard, and recorded in their 

 logs, a loud cannonade which they heard on a particular day, and it 

 was afterwards found, by a comparison of the logs of the ships, that 

 this very cannonade proceeded from the proving of large pieces of 

 ordnance which had been conducted for the greater part of a day, at 

 a dock yard, in the vicinity of one end of the fleet, from which the 

 other end, at which the reports were heard, was distant (if the re- 

 porter heard correctly,) some hundreds of miles. Dr. Reid then 

 showed how the reverberating of sound, from the ceiling, walls and 

 floor of a room, by being continued too long, and interfering with 

 each other, would have the effect of producing a confusing noise, 

 and thus interfering with the hearing of the succeeding parts of the 

 discourse. 



He concluded that low roofs to buildings, and consisting of many 

 planes, set at various angles, rough and interrupted walls, and a floor 

 possessing very little resilience, such as earthen floors do, or, if 

 boarded, then much broken and interrupted by irregular seating, pro- 



