September 23, 1920] 



NATURE 



123 



complete, and is merely a compilation of some 

 sectional lists ; the paging shows how much is 

 missing. In the sections for barometer and thermo- 

 meter the lists do not give the self-recording instru- 

 ments, although in rainfall and wind the registration 

 instruments are fully dealt with. The section for 

 deep-sea thermometers well illustrates the advantage 

 secured by the long association of the optician with 

 special scientific instruments ; these thermometers 

 have been c^irefully watched and improved by the 

 maker for about half a century. Sunshine instruments 

 of two recognised forms are well described and com- 

 pared : the " Campbell-Stokes " recorder burns a 

 trace on a time-divided card by the impinging of the 

 sun's rays focussed through a sphere of glass; this 

 >ystem is generally adopted by the Meteorological 

 Office. The other form is the "Jordan " recorder, in 

 which a photograph of the rays of the sun is obtained 

 upon a specially sensitised chart. The catalogue will 

 be forwarded by Messrs. Negretti and Zambra to any- 

 one who may be interested. 



.\ccORDlNG to an article by M. Jacques Beyer in La 

 Salute for September 4, the aerotechnical institute 

 wf the Military Academy at Saint-Cyr has installed a 

 pneumatic tank for experiments on the effects of 

 reduced air-pressure and temperature on the physical 

 powers of aviators. The tank in use up to the 

 present time is 2 metres in diameter and nearly 

 4 metres long. It is of steel 5 mm. thick, and is 

 insulated thermally by an outside layer of cork lo cm. 

 thick. Four glazed portholes are provided, through 

 which the officer in charge can observe the aviator 

 under test inside. Air-pumps and an air-refrigeration 

 plant are provided, so that the pressure and tempera- 

 ture of the air in the tank can be varied at will. 

 O.xygen tubes are also available, and the interior and 

 • \terior of the tank are in communication by tele- 

 hone. By the help of this tank Dr. Garsaux has 

 r.en able to study to what altitude aviators could 

 isc<-nd without losing their skill or injuring them- 

 ~'lv.^, and at what stage of the ascent oxygen should 

 1h supplied. These altitudes differ according to the 

 temperament of the aviator, but 6000 metres appears 

 to be the limit f<^ even the best men, and oxygen 

 liecomes necessary at 3500 or 4000 metres. Further 

 observations are to be made with a larger tank. 



.A L'SEFUL account of the "synthetic" drugs is given 

 by Prof. J. T. Hewitt in a series of Cantor lectures 

 recently publish<"d (Journal of the Royal Society of 

 Arts, .\ugust 13 and 20). Strictly, the phrase 

 synthetic drugs," implying as it does that the sub- 

 -t.inces in question arc produced artificially and find a 

 use in medicine, would include many (airly simple 

 rompounds, such as chloroform ; but in practice it is 

 restricted to more or less complex carbon compounds 

 which are either prepared by truly synthetic methods 

 {e.g. veronal, phenacelin), or obtained by modifying 

 the structure of naturally occurring compounds 

 through chemical treatment. Thus morphine is con- 

 v<»rlrd into codeine (methyl morphine) or into heroin 

 ffli.irrtyl morphine) by appropriate chemical reactions. 

 1 ' lecturer classifies the various products accord- 

 NO. 2656, VOL. 106] 



ing to their chemical relationships as derivatives of 

 hydrocarbons, alcohols, ketones, and so on, thus ob- 

 taining a systematic survey of the various groups. 

 The descriptions of the drugs are supplemented by 

 outlines of the methods of manufacture, and in many 

 instances include notes on the history and literature. 



A SIMPLE form of thermo-electric pyrometer, mainly 

 intended for use with electric resistance furnaces, has 

 been placed on the market by the Automatic and 

 Electric Furnaces, Ltd. The thermo-couple is com- 

 posed of wires of nickel and nickel-chrome alloy, 

 these metals being chosen owing to their resistance 

 to oxidation at temperatures not exceeding 1000° C. 

 The E.M.F. developed by this couple is only about 

 one-half that furnished by a junction of iron and 

 constantan, but is still sufficiently high to enable a 

 pivoted indicator to be used. In order to avoid cold- 

 junction errors, the leads to the indicator consist of 

 the same materials as those of the thermo-couple — a 

 procedure now followed generally in the case of base- 

 metal junctions. In a leaflet issued by the firm an 

 account is given of experiments performed with the 

 view of determining the lag caused by the use of thick 

 wires, and also that due to the use of a pwotecting 

 sheath. The results show that notable errors may 

 arise by assuming that a sheathed junction closely 

 follows the changing temperature of a furnace, parti- 

 cularly when thick wires are used ; and it is concluded 

 that the wires should be as thin as possible — consistent 

 with sufficient strength— and, when permissible, 

 should be used uncovered. Two types of instrument 

 are made : one with the junction unprotected, and 

 intended for use in a clean atmosphere ; and the other 

 provided with a silica sheath for use in salt-baths, 

 wires of No. 20 gauge being used in each. Both 

 forms should prove useful for the class of work for 

 which they are intended. 



.Arranged by the Institution of Petroleum Techno- 

 logists, an interesting lecture on petroleum refining 

 was given on September 8 by Dr. \. E. Dunstan. 

 Crude petroleum is a very complex mixture of sub- 

 stances, which are most conveniently utilised if 

 separated into groups (petrol, " w-hite spirit," kero- 

 sene, fuel-oil, and so on) according to their volatility. 

 One object of refining is to effect this separation; n 

 second is to remove impurities, colour, and odour from 

 the products. Probably in the future physico-chemical 

 methods rather than purely chcniical tr<-atnient will 

 be relied upon for the removal of impurities. Sulphur 

 compounds in particular arc mentioned as substanics 

 which arc adsorbed by passing oil distillates through 

 a column of bauxite or fuller's earth, or, alternatively, 

 by passing the vapour of the oil over heated bauxite. 

 A fact not very generally known is that "toluol " 

 (toluene), so urgently wanted in the war period, 

 occurs naturally in certain varieties of crude 

 petroleum, and " innumerabk; tons" of it were, 

 indeed, obtained from this source. It is much purer 

 than the toluol extracted from coal-tar, and the lec- 

 turer predicts a " future " for the aromatic hydfo- 

 carbons yielded by petroleum. Toluol can also be 

 manufactured by "cracking" petroleum— that i >, 



