376 Mr Gobbett, On the Heat generated by Fibrous Substances, etc. 



mediate neighbourhood of the spores has registered over 100° C. 

 for 9 minutes, and over 125° C. for 5 minutes. It is therefore 

 clear that extreme dryness may interfere with the sterilisation of 

 such things as are composed of organic fibrous material, and it is 

 important to know whether in practice such a state of dryness 

 ever occurs. Probably in our climate it does not, for though it has 

 already been stated that a temperature considerably over that of 

 the breath (37° C.) may be registered in the mouth by blowing 

 the expired air through a few rolls of one's pocket-handkerchief 

 enclosing a thermometer without any preliminary drying what- 

 ever, I have never seen a temperature of over 100° attained in 

 rolls of flannel, cotton or paper, exposed to saturated steam, 

 unless these materials have previously been artificially dried. 

 But it must be added that the experiments were made in the 

 damp atmosphere of an English November, and they by no means 

 show that heat cannot be generated, and the steam thereby 

 superheated within the material and its sterilising properties 

 diminished in the dry atmosphere of hotter countries, or even 

 perhaps in this country during the summer. This point is still 

 under investigation. 



A Method of Measuring the Retardation produced by a 

 Crystal Plate. By Mr L. R. Wilberforce. 



[Bead 21 May 1900.] 



