Item 124 - Letter from Alexander Burnett

Mill Hill College, Stonehaven N.B. - AB sends WW a few remarks on latent heat to show 'that the doctrine hitherto inculcated on that subject is not altogether unassailable'. He describes an experiment involving two vessels, one containing a pint of water, the other ten pints, both at 40 degrees, and heated by a flame of equal power. The thermometer in the small vessel is always a ten times higher degree of heat than the thermometer in the larger vessel. Since the same amount of heat is going into the latter it must contain the same amount of heat: 'all the heat is there and all perfectly free or active - its activity only being as regards its influence on the thermometer'. If 'this vessel could be compressed into a tenth part of its space then the thermometer would indicate a five times higher degree of heat'. AB next turns his attention to steam and concludes: 'water when converted into steam expands into 1700 times as much; - a pint of water converted into steam occupying a space equal to 1700 pints. Now, - as the steam as well as the water at 212, here, you have on the one hand, a heating substance (the boiling water,) containing a pint of heat of 212 degrees, and on the other hand, a heating substance (the steam) containing 1700 pints of heat at 212; - and if these two substances are severally incorporated in a gallon of water, is it to be wondered at, that the gallon in which the 1700 pints of heat not condensed, should possess the much greater quantity of heat - The wonder should rather be in this, - that the increase only of heat in the gallon of water in which the 1700 pints of steam it condensed, instead of being in the proportion of 1700 is only 1000, - a circumstance which to me went to prove not only that there is no heat in a state of latency in steam, but that in any given quantity of steam say a pint at 212 - there is less heat in point of volume than in an equal quantity of water at the same temperature, - in the proportion of 1700 to 1000'.