NA TURE 



[July 22, 1922 



turns on its axis. A 60-foot pendulum, suspended 

 from the centre of the dome, will be set swinging 

 through a long arc, repeating the celebrated experiment 

 Hi Foucault. The swinging pendulum will mark an 

 invariable direction in space, and as the earth of the 

 building revolves beneath it, rotation will be plainly 

 shown by the steady change in direction of the 

 pendulum's swing over a divided arc. 



Two great phenomena of Nature, the sun and the 

 rotation of the earth, are thus to be exhibited. Other 

 phenomena to be demonstrated in striking form in 

 the central rotunda are magnetic storms, earthquakes, 

 gravitational pull of small masses, the pressure of light; 

 the visible growth of plants, swimming infusorians 

 in a drop of ditch water, living bacteria, and other 

 interesting phenomena. 



In the seven exhibition rooms surrounding the 

 central rotunda, the latest results of scientific and 

 industrial research will be illustrated. One room will 

 be se1 aside for the use of Government bureaus, another 

 for industrial research laboratories, others for the 



laboratories, observatories, and research institutes 

 of universities and other institutions. The newest 

 discoveries and advances in the mathematical, physical, 

 and biological sciences and their applications will be 

 shown in this living museum, in which the exhibits will 

 be constantly changing with the progress of science. 

 One week there may be displayed the latest forms of 

 radio-telephony ; the next perhaps a set of psychologi- 

 cal tests or a new find of fossils or a series of synthetic 

 chemical compounds. Such a mutating museum will 

 continue to attract and instruct large numbers of 

 visitors and residents. 



We call it the building for the National Academy of 

 Sciences and the National Research Council, but in 

 reality it should be the national home of science in 

 America, and will be looked upon by our fellow-citizens 

 and the world at large as the place where the creative 

 mind will be able to do much to bring about a better 

 existence for the future people of the world, for it is 

 to their enlightenment and advancement that it will 

 be dedicated. 



The Internal Combustion Engine. 1 



By Prof. W. E. Dalby, F.R.S. 



The Influence of the Internal Combustion Engine. 



TO engineers the terms horse -power and horse- 

 power hour have strictly technical meanings. 

 They <an be illustrated by comparing the weight 

 and efficiency of an aircraft engine and a loco- 

 motive engine. An aircraft engine can be built with 

 about 2I lbs. of metal per horse-power as against 

 approximately 250 lbs. of metal per horse-power in a 

 locomotive engine. An aircraft engine requires about 

 I lb. of fuel oil per H.P. hour as against 3 lbs. of coal 

 per H.P. hour used by the locomotive engine, in 

 addition to which the locomotive engine must carry 

 about 3 gallons of water per H.P. hour. All these, of 

 course, are round figures. It is the extreme lightness 

 of the petrol engine in relation to its power which lias 

 made it possible to develope aircraft. 



An internal combustion engine of the Diesel type is 

 built to use heavy oils, and has provided a prime mover 

 by means of which the submarine was able to develop 

 so considerablv during the war. Thus the internal 

 combustion engine helped to sink our food ships, but 

 at the same time helped to save the situation by driving 

 the agricultural tractor. Few, perhaps, realise fully 

 how serious was our position in 191 7. Horses were 

 required for the Army and were being taken from 

 the farms ; but the agricultural tractor replaced them 

 at the plough and thus made it possible to maintain 

 the necessary food supplies. 



Probably the greatest effect of the internal com- 

 bustion engine on our national life is its influence on 

 road transport. Standing at Hyde Park Corner 

 twenty years ago a motor car would have excited 

 notice ; standing there to-day it is almost true to say 

 that the horse-drawn vehicle has practically dis- 

 appeared. The internal combustion engine is displac- 

 ing the horse from the streets, and is even causing the 

 railway companies grave concern. The chairman of 

 one of them stated at the last half-yearly meeting that 



1 From ,1 Discourse delivered at the Royal Institution on Friday, May < . 

 NO. 2 7St, VOL. I lOJ 



the companies had lost 9 million tons of goods, and 6 

 million passengers to the motor lorry and the motor 

 car. This is a remarkable achievement for the small 

 16-20 H.P. internal combustion engine which is fitted 

 in these vehicles. During 1921 about 800.000 licences 

 were issued to vehicles propelled by internal com- 

 bustion engines and the tax on them amounted to 

 about ten million pounds. 



These brief considerations indicate how profound has 

 been and is the influence of the internal combustion 

 engine in shaping our destinies. It has conquered the 

 air, and has given us a prime mover useful in farming 

 and in transport. It is influencing the policy of our 

 railways, and will shortly so transform our outlook and 

 our modes of life that men of to-day will appear to be 

 separated from their boyhood not by a few decades 

 but by a few centuries. 



Some Problems of the Internal Combustion Engine. 



Considering combustion from the point of view of 

 the Kinetic Theory of gases, but without attempting 

 to explain the nature of the differential attraction 

 between molecules, most of the energy developed in 

 the cylinder of an internal combustion engine arises 

 from the fact that oxygen combines with carbon and 

 hydrogen to develop large quantities of heat. The 

 function of the engine is to convert as much as possible 

 of this heat into mechanical work. 



It can be deduced by the laws of gases that the 

 molecules at 22° C. and atmospheric pressure require 

 729 times the volume they occupied as a liquid. This 

 can be illustrated by "air patterns" representing the 

 distribution of molecules in the air. Actually the mole- 

 cules are flying about at a high velocity across the 

 vessel the sides of which they are continually bombard- 

 ing and therefore exerting pressure on them. 



Calculation from the kinetic theory of gases shows 

 that at 22 C. the oxygen molecules in the air are flying 

 at a velocity of about 1600 ft. per second, the nitrogen 



