NATURAL PHILOSOPHY. 219 



IIIXTS OX VEXTILATIOX. 



Why do we want ventilation ? Why do we want fresh air ? Why do we 

 want to take in oxygen ? And why do we want to get rid of carbonic acid ? 

 Shortly, we want oxygen because of its chemical energy it is the main 

 spring of our life. On it the production of animal heat depends, and the vital 

 powers sensation and motion, no less than nutrition and secretion, are 

 directly influenced by its action. 



Why do we want to get rid of surrounding carbonic acid? Literally, 

 because the carbonic acid stops the way, and prevents the escape of newly 

 formed carbonic acid from within. If we were placed in an atmosphere con- 

 taining as much carbonic acid as exists in the lungs, the carbonic acid of the 

 atmosphere would not pass from the lungs to the blood and act as a poison, 

 but that carbonic acid which was passing out from the blood would stop in the 

 lungs and prevent more from escaping out of the blood, and that carbonic 

 acid which was formed in the body would act as a narcotic poison. From ex- 

 periments on animals, it appears that the air must contain 20 per cent, of car- 

 bonic acid before absorption of that gas by the blood is observed. Moreover, 

 the escape of gases from the blood affects the circulation of the blood. In 

 sudden death from suffocation, the side of the heart which throws the blood 

 to the lungs is found distended, whilst the side which throws the blood from 

 the heart is empty ; there has been obstruction in the flow. By stopping 

 respiration and causing pressure we can stop the pulse and the heart's sounds 

 and impulse when we please. This is more the result of pressure than of any 

 arrest of escape of carbdnic acid, and is a striking evidence how suddenly the 

 action of the heart may be influenced by the respiration. When the escape 

 of carbonic acid from the blood is retarded or prevented, the want of ventila- 

 tion of the blood causes more or less stoppage of the blood in the vessels, and 

 makes the blood a narcotic poison to all the tissues with which it is in contact. 

 We may consider oxygen as our most necessary food, and carbonic acid as 

 the refuse which passes into our sewers. We all fully believe that a house 

 badly drained causes disease and death, but will scarcely admit to ourselves 

 that a house or body without good means of ventilation is a house or body 

 badly drained. At present our chimneys are our chief aerial drains, which 

 almost cease to act as soon as the temperature outside and inside the house is 

 the same ; and even when these drains are in action, we are unwilling to 

 think that that fire which ministers to our warmih, like most contrivances for 

 doing two things at once, does neither well. From a Paper read by H. JBence 

 Jones, J/ Z>., before the Royal Institution of England, April 18, 1856. 



% 

 SELF-REGISTERIXG ANEMOMETER. 



Mr. Welsh. Superintendent of the Kew Observatory, exhibited and de- 

 scribed to the British Association a model of a self-registering anemometer, 

 invented by Mr. Beckley. In this Mr. B. has adopted Dr. Robinson's method 

 of measuring the velocity of the wind by the rotation of a system of hemisphe- 

 rical cups, the direction being indicated by a double wheel fan like the 

 directing vane at the back of a windmill. A stout tubular support carries 



