SECTIONAL TRANSACTIONS.—A, G. 289 
surface of a partial insulator covering a heated body. In other words, the 
cloth sample is placed over an artificial ‘skin’ covering a warm. artificial 
“human body’ in the form of a heated water container, and the temperature 
variations at points underneath the clothing and on the surface of this 
artificial ‘ skin’ are measured. 
It is found that the ‘ skin’ temperature rises when clothing is placed over 
it, the rise in temperature being measured by differential thermopiles. 
From this we calculate variations of heat retention as percentages of 
complete insulation, having independently developed the method of calcula- 
tion previously used by Barker. 
The advantage of this experimental method is that the effects due to 
variation in the tension by which the samples are stretched can be examined, 
also variations due to changes in wind velocity. 
Mr. G. P. Crowpen.—The use of bright metallic surfaces for increasing 
human comfort in the tropics. 
A comfortable, clothed, sedentary individual produces some 400 B.Th.U. 
per hour by reason of the chemical changes associated with living processes, 
circulation, respiration and glandular activity. In still air at 60° F. and 
50 per cent. humidity, roughly 45 per cent. of this heat is lost by radiation. 
At 80° F. loss by radiation is approximately halved, while under tropical 
conditions a gain of heat by radiation from the surroundings necessitates 
increased loss by evaporation of sweat to keep the body temperature normal. 
Human comfort in the tropics can be increased by any means of reducing 
heat gain by radiation. ‘The well-known physical properties of high 
reflectivity and low emissivity for radiant heat possessed by bright metallic 
surfaces can be made use of for this purpose. It has been shown that if 
an air space of 1 in. is divided medially by a layer of bright metallic air- 
proof material, known as reinforced aluminium foil, the passage of heat 
across the space is as effectively hindered as if 1 in. of cork or 13 in. of brick 
were used. ‘This insulation has been used in tropical helmets, galvanised 
iron hutments and tents, and laboratory and field tests have proved its 
value for increasing human comfort. 
Mr. S. G. Barker.—The interpretation of physical data regarding textiles 
in terms of bodily comfort. 
The analysis of the figures obtained for a large variety of fabrics made 
from different textile materials indicates that fabric structure and thickness 
is of paramount importance. 
The paper is extended to the question of hygienic coverings during 
sleeping and the manufacture of beds and bedding. 
Physical data are quoted in support of the arguments put forward, and 
definite inferences are drawn regarding ideal conditions from the physicist’s 
point of view for realising bodily comfort. 
Dr. M. C. Marsu.—The interchange of heat as affecting clothing material. 
The paper is a review of the heat interchange processes which occur when 
fabrics are used as thermal insulators under the conditions normally obtain- 
ing in clothing. Fabrics in general have a rough surface owing to the 
method of their construction, and the effect of this on heat interchange is 
first considered and shown to be of primary importance. 
When a large number of results is available, the general effects of air 
permeability and the ability to transmit radiation can be determined. In 
