418 SECTIONAL TRANSACTIONS.— TEXTILES. 



stretch-load diagram is shown by the relation b =k (■*- ) which is used to cor- 



V V,. ) 

 rect the experimental measurements for irregularities in manufacture. 



The relations between the equation constants and the size of yarn, twist, length 

 of specimen and rate of loading have been worked out. These may be used for 

 correction of the effects of variants in yarn structure and so allow the effects of 

 different kinds of fibre on the characteristics of the stretch-load diagrams to be 

 determined. The constant b, is definitely shown to measure the effect due to slip 

 of the fibre in the yarn, and large differences in this respect are shown to exist between 

 different kinds of flax and hemp. 



The general conclusion is that the longitudinal extension of flax yarns is a com- 

 bination of several effects, the chief of which are indicated as a tightening up of the 

 fibre strands on one another, the slip of the fibres past one another, elastic stretch of 

 the fibre, and possibly permanent elongation of the fibre. The diagrams are similar 

 in type for all kinds of flax yarns tested in the air dry condition, and there is no 

 evidence of an increased rate of extension before breakage, so it is inferred that yarn 

 breakage is mainly attributable to rupture of the fibre and fibre bundles and not 

 excessive slippage. The conclusions drawn from tests employing a low constant rate 

 of loading are confirmed by tests in which repeated applications of small stresses were 

 employed. The bearing of these conclusions on the investigation of important 

 practical problems is discussed. 



REFERENCES. 



G. F. New, J. Text. Inst., 1922, 13, No. 2 ; 1926, 17, No. 9. 



G. F. New and A. L. Geegson, J. Text. Inst., 1923, 14, No. 11. 



J. A. Matthew, J. Text. Inst., 1922, 13, No. 2 ; 1926, 17, No. 3 ; 1927, 18, No. 6. 



Dr. Ezer Griffiths, F.R.S. — ''Air Conditioning ' Experiments, and some 

 Special Forms of Hygrometers. 



An account is given of various researches bearing on ' air conditioning.' One 

 problem was to devise means of controlling the humidity in rooms for the storage of 

 fruit and eggs when the temperature was below normal atmospheric. The system 

 employed was to circulate the air through brine spray and, since the density of the 

 brine solution determined the vapour pressure, an automatic arrangement was 

 devised to maintain the concentration within narrow limits. 



Another investigation was concerned with the study of the cooling effect obtained 

 with ducts placed on the external wall of a fruit stores : the air being circulated 

 through the ducts either by natural convection or by forced air circulation. A duct 

 whose surface was covered with moistened cloth gave a fourfold cooling effect com- 

 pared with an uncovered duct. Ducts of various sections were also investigated. 



Since the control element in several types of air-conditioning appliances is a 

 material whose length varies with changes of humidity, a convenient form of 

 apparatus has been devised for testing ten specimens simultaneously, and the results 

 of tests are given in the paper. 



A number of hygrometers are described which have been devised to meet special 

 requirements, (a) The ' fog formation ' hygrometer is based on the principle that 

 fog forms in an atmosphere which is adiabatically expanded : the amount of 

 expansion necessary for a fog which is just visible is a function of the humidity. 

 (6) The resistance thermometer form of wet and dry bulb hygrometer described has 

 an extremely small time lag. Cotton-covered wire carried on a glass frame is 

 periodically dipped in water. The difference in temperature between wet and dry 

 bulb is recorded by a string galvanometer, (c) The portable dew-point apparatus is 

 a differential air thermometer, one bulb of which is so designed that it can be cooled 

 by a stream of cold C0 2 ; the dew is observed on a polished portion of the bulb 

 surface, {d) The ' cellophane ' hygrometer is based on the change in weight with 

 humidity of thin cellophane sheet, (e) The hygrometer for timber seasoning kilns is 

 a wet and dry bulb hygrometer employing mercury in steel thermometers with both 

 pointers indicating on the same dial. Arrangements are made for drawing air past 

 the bulbs and for maintaining the covering over the wet bulb saturated with water. 



The appendix to the paper contains a description of some typical air-conditioning 

 installations of the water spray type. 



Dr. L. L. Lloyd. — Rancidification and Oxidation of Olive Oil. 



