'April. 22, 1920] 



NATURE 



245 



is a camphor glass or chemical weather glass, long 

 acknowledged to be of no real scientific value. The 

 report for 19 18 deals with the corrections to Be applied 

 to the readings of an unaspirated wet-bulb thermo- 

 meter in an " Indian " shelter to reduce them to those 

 of an aspirated thermometer at definite wind velocities 

 and for different depressions of the wet bulb. With 

 the lighter wind velocities, of 1-5 m.p.h., and for the 

 larger depressions of the wet bulb, say amounting to 

 6°-io°, the subtractive correction to the unaspirated 

 wet bulb amounts to 1° or slightly more. Three 

 thousand three hundred and seventy-five observations 

 have been dealt with, but as yet no definite scheme 

 has been decided upon. The matter has been con- 

 sidered in correspondence with the British Meteoro- 

 logical Oflfice. 



Milk Production of Ayrshire Cattle. 



'T^HE critical genetic study of a character such as 

 •*• that of milk production in cattle, which is 

 highly subject to environmental influences, cannot be 

 carried out effectively until a fairly comprehensive 

 knowledge of the normal variation of the character 

 has been acquired. To this end Prof. Raymond Pearl 

 and Mr. J. R. Miner have carried out a biometrical 

 analysis of the normal individual variation in the 

 milk flow and the fat content of the milk of Ayrshire 

 cattle, the results of which are summarised in a con- 

 tribution to the Journal of Agricultural Research 

 (vol. xvii.. No. 6). Their study is based on the records 

 of Ayrshire cattle for the years 1908 and 1909 pub- 

 lished in the reports of the Ayrshire Cattle Milk 

 Records Committee of Scotland, more than three 

 thousand records in each year being used for the 

 purpose. Amongst the many important conclusions 

 arrived at mention may be made of the indications 

 that about one-half of the observed variation in milk- 

 production results from the varying genotypic indi- 

 viduality of the animals with respect to this character, 

 the remainder resulting from varying environmental 

 influences. The udder as a secreting organ is com- 

 pared with the oviduct of a hen, and it is shown that 

 the latter operates with somewhat less variability than 

 the former, having regard to the absolute weight of 

 the product in the two cases. 



The change in mean weekly yield of milk with 

 advancing age is found to be represented by a 

 logarithmic curve, the absolute amount of milk pro- 

 duced per unit of time increasing, though at a decreas- 

 ing rate, with the age of the cow to a maximum, 

 which was found to be when the cow is ten to eleven 

 years old. The mean fat percentage of the milk was 

 found to decline with advancing age until the tenth 

 year ot the cow's life, after which it remains about 

 constant. 



The Ignition Points of Liquid Fuels. 



T N a paper read before the Institution of Petroleum 

 ^ Technologists on January 20, Mr. Harold 

 Moore described a number of determinations of 

 the ignition point of commercial fuels which are, or 

 might be, used in internal-combustion engines. His 

 ignition meter, somewhat similar in principle to that 

 designed by Holm, consists of a steel block, heated 

 from below, in the upper surface of which a hollow 

 is made to take a crucible of platinum, nickel, or 

 quartz. The air or oxygen supply passes through a 

 hole in the block before entering the crucible, so as to 

 pre-heat it to the temperature of the crucible, which 

 is given by a resistance thermometer placed in a hole 

 drilled in the block near the crucible. A cover to 



NO. 26^4, VOL. lOt^l 



protect the crucible from draughts is screwed on to 

 the block, and a drop of the liquid fuel is introduced 

 through a hole in this cover and falls on to the 

 bottom of the crucible. After an interval, more or less 

 prolonged, an explosion is heard and a flame seen if 

 the temperature is above the ignition point. This 

 interval may be as long as thirty seconds or more, and 

 there is no doubt that quiet combustion takes place 

 during this period, and such combustion is very 

 marked in the case of ether. On the other hand, the 

 evaporation of the drops of liquid must produce local 

 cooling, and, unless the fuel is quite homogeneous, the 

 ignition point found must in many cases be that of 

 the last portion to evaporate. 



But, in spite of certain inherent defects, the method 

 gives a valuable comparative test of different fuels — a 

 test which is quick and easy to apply. 



Mr. Moore recommends the use of ordinary com- 

 pressed oxygen instead of air as giving more con- 

 cordant results and as having a concentration* at 

 atmospheric pressures more nearly like that used in 

 motor engines. Most hydrocarbon'liquids tested in air 

 gave ignition points from 100° C. to 200° C. higher 

 than in oxygen ; but, curiously enough, Mr. Moore 

 found that in an atmosphere containing 70 per cent, 

 of carbon dioxide and 30 per cent, of oxygen the igni- 

 tion point of kerosene was almost the same as in pure 

 oxygen. A few ignition points from Mr. Moore's lists 

 may be quoted : " 



Ignition Point. 



Fuel In oxygen In air 



° c. ° c. 

 Taxibus spirit (Anglo-American 



Oil Co.) 272 390 



Anglo-Persian oil 254 408 



Anglo-Mexican oil 259 417 



Normal hexane 287 — 



Benzene 620 • — 



Ethyl alcohol 395 518 



Ether (methylated) 190 347 



In silica 

 crucible 



Hydrogen — 678 



In the case of mixtures of two liquids of very 

 different ignition points the addition of about 20 per 

 cent, of the more easily inflammable liquid suffices 

 to reduce the temperature substantially to that of the 

 lower constituent ; for instance, the addition of 20 per 

 cent, of ether (ignition point 206°) to xylol (ignition 

 point ^55°) reduced the ignition point of' the mixture 

 to 246°. 



Naval Research and Experiment. 



'X'O ensure that the full benefits of science shall be 

 ■*• secured to the Naval Service, a Department of 

 Scientific Research and Experiment has been set up 

 under the Third Sea Lord and Controller. As the 

 Scientific Adviser of the Admiralty, and in charge of 

 this Department, Mr. F. E. Smith, F.R.S., has been 

 appointed with the title of Director of Scientific 

 Research. It is the duty of the Department to keep 

 the Navy in touch with outside scientific establish- 

 ments and to ensure that the work at the various 

 naval experimental establishments proceeds with fCill 

 cognisance of scientific progress and methods. The 

 Director of Scientific Research will work in close 

 association with the Naval Staff, thus ensuring that 

 naval policy is framed with due consideration of the 

 possible practical applications of scientific progress 

 in relation to naval needs, and enabling requireinehts 

 as to types and weapons to be formulated with a 

 knowledge of the latest scientific possibilities. 



