604 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



harmonize in time with the vibratory action due to the elasticity of the 

 timber. Many points connected witli the subject of secondary vibrations 

 are yet to be further elucidated by experiment. 



.Light from Rapid Dilations. 



Only one other cause for a^tli undulations by means of carbon can now 

 be suggested. It arises from the characteristics and conditions of the 

 three important simple bodies which play the principal parts during ordi- 

 nary combustion. Oxygen, the clement of which more than one-half of our 

 globe is composed, when isolated, is a permanent gas. No power yet 

 applied has reduced it to the liquid state. Hydrogen, a gas sixteen times 

 lighter than oxygen, has also no cohesive power, Natterrer, of Vienna, 

 subjected these gases separately to a pressure of 3,000 pounds to the square 

 inch, when at a temperature of lOG deg. centigrade below the freezing 

 point of water, without producing cohesion. Yet these two gases, when 

 mixed in the proportion of two volumes of hydrogen to one of oxygen, are, 

 by the electric spark, instantly condensed to steam, and, on cooling, to 

 water. Carbon, on the other hand, when isolated, is always a solid No 

 amount of heat yet applied has brought it to a gaseous, or even a liquid 

 state. In its most condensed conditittn, as the diamond, it had 3.56 times 

 the specific weight of water. It is 41,890 times heavier than an equal 

 bulk of hydrogen, 2,618 times heavier than oxygen, and 2,992 times 

 heavier than olefiant gas (C4 II4. ) 



In the process of illumination by the combustion of hybro-carbon gases, 

 as described, the isolation of the carbon seems to be essential. It must, 

 therefore, instantly change its volume and become a solid, and then as 

 quickly assume the gaseous state, in the formation of carbonic acid gas. 

 These rapid contractions and expansions of carbon may act as pulsations 

 on the pervading a?th, and thus generate the whole series of waves, which, 

 commingling, form white light. 



It is passing strange that carbonic acid gas, a resultant in generating 

 light and heat — including the vital heat <A' myriads of animals — should, 

 after its passage from the lamp or the lung to the leaf, be resolved into 

 carbon and oxygen by a force similar to that these constituents can exert 

 under certain conditions. 



Molecular Forces. 



Turning again to the Highland Lighthouse, let us estimate the power 

 expended by its lamps. The average weight of oil consumed nightly was 

 about sixteen pounds at the time of Thoreau's visit. Taking the mean of 

 the results of experiments by Favre, Silbermann, Dulong, and Andrews 

 with olefiant gas (oil gas not being given), Ave find that 11,943 jiounds of 

 water are raised 1*^0 by the combustion of one pound of oil. This sum 

 multiplied by sixteen, the number of pounds used per night, and that pro- 

 duct by 1,390, the number of foot-pounds which measures the force ex- 

 pended in raising one pound of water 1*^0 — that being the mechanical 

 eqtiivalent of heat as correctly determined by Mayer in 1842 — we have 

 265,012,320 foot-pounds as the amount of energy expended in generating 

 the light required for a single night. 



