Feb. lo, l88S.] 



SCIENTIFIC NEWS. 



129 



THERMIC VENTILATOR. 



THE desideratum in ventilation is that the aerial con- 

 tents of a room should be in continual and regular 

 motion of displacement and renewal, the renewal taking 

 place at the rate of at least 2,000 cubic feet per hour for 

 every occupant. The displacement should also be so 

 •conducted that no current should be felt, and that a 

 uniform temperature should be maintained, while at the 

 same time it is completely under control. With these 

 principles in view, Mr. Lawson Tait, the well-known 

 surgeon, of Birmingham, has introduced a very simple 

 and efficient little apparatus, which he terms a thermic 

 s/entilator, and which can be used instead of an or- 



dinary fire. On referring to the accompanying illus- 

 tration, it will be seen that there is a vertical tube with 

 a gas burner inserted in its lower end. Inside this 

 tube there is another tube shown in dotted lines, 

 which is open at both ends, the top of the outer tube 

 being closed, and having a horizontal outlet leading into 

 the chimney flue. When the gas-jet is alight the tubes 

 become heated, and a circulation of air is set up through 

 the inner tube, the products of combustion passing 

 off into the chimney flue. In this way the air of the 

 room in which the apparatus is placed is warmed and 

 circulated, while it is not contaminated by the products 

 of combustion. Fresh air can be brought from the out- 

 side of the house, or from any convenient spot, and the 

 vitiated air can be removed by means of a suitable outlet. 

 One or more jets of gas can be used, according to the 



size of the apparatus, and it is roughly calculated that 

 for every cubic foot of gas burned, one thousand cubic 

 feet of fresh air can be drawn into the room, and of 

 course the same quantity will be driven out. The little 

 side burner shown in the illustration is to provide a small 

 flame, which prevents the larger atmospheric flame from 

 being extinguished by a down-draught, and this is a 

 very essential adjunct. The apparatus is made by 

 Messrs. Taunton and Hayward, of Heaneage Street, 

 Birmingham. 



WEIGHTS AT DIFFERENT AGES. 



THE interesting investigation of Mr. Francis Galton on 

 the record which has been kept by Messrs. Barry, of 

 the weights of their customers for more than a century, 

 was described on page 225 in our December number. 

 The results may be very clearly expressed by a set of 

 curves, and afford a good example of the value of the 

 graphical method for exhibiting the variation of two 

 quantities, and of the relations between different varia- 

 tions. We do not know if Mr. Galton has already 

 plotted these curves ; it is, however, probable that he has. 

 In the accompanying table twenty years to an inch are 

 taken on the horizontal scale, and twenty pounds to an 

 inch on the vertical. The effects of good living on the 

 aristocracy at the beginning of the century is shown in a 

 striking manner by the rapid ascent of the first curve. 



30 35 40 45 



Sj 60 65 70 



It is noticeable that during their second quarter century 

 in the second and third period, Messrs. Barry's customers 

 gained weight at the rate of ten pounds in twenty-five 

 years, or a little over half an ounce per month, with 

 remarkable regularity, but the difference in their old 

 age calls for further explanation. No reason is apparent 

 why no one in the second period attained the weight ot 

 thirteen stone, but it is very satisfactory to see that in 

 the third period, the constitutions were sound enough at 

 fifty to allow of a steady though rather more rapid 

 increase. It would be very interesting to compare these 

 curves with those of the labouring classes during the 

 same period, and to compare the changes in weight- 

 making with the changes which have been observed in the 

 distribution of wealth. It is probable that the weight of 

 the working man would show as favourable changes during 

 the century, as are found among the leisured classes, but 

 in the reverse order. 



