February 2, 1922] 



NATURE 



151 



coil design is that it allows the milli-ampere meter to 

 be inserted at the mid-point, which is at zero potential, 

 and hence the instrument can be brought to an 

 ordinary low-tension switchboard. 



An account of the discussion on the future of geo- 

 metrical optics which took place at the Cambridge 

 meeting of the Optical Society in May last is given 

 in part 5 of the Transactions of the society for the 

 present session. On the whole, the representatives 

 of the manufacturers were in favour of retaining the 

 step-by-step trigonometrical method of tracing rays 

 through the system under design in order to get rid 

 of aberrations rather than changing to the analytical 

 methods, which give the aberrations of the first order 

 in terms of a certain quartic in the magnification and 

 those of the second order in terms of 



M(i + AM)/(i + BM), 

 where A and B are constants and M is the square of 

 the inclination of the ray to the axis. It was, how- 

 ever, suggested that some attempt should be made 

 by mathematicians to reduce the complexity of the 

 formulae involved by bringing the subject into line 

 with the wave theory. It was pointed out that the 

 British optical trade must in the next four or five 

 years improve its optical designs if it is to be able in 

 the future to sell its products against the better 

 designed articles offered by manufacturers of other 

 countries. 



k LIST of American research chemicals has been 

 issued as No. 23 of the Reprint and Circular Series of 

 the National Research Council, Washington. The 

 list includes biological stains and indicators, and in- 

 cludes a very large number of fine chemicals. The 

 number is larger than that in the corresponding list 

 of British research chemicals, issued by the Associa- 

 tion of British Chemical Manufacturers, but the latter 

 is incomplete, and although not dated, was issued 

 some time before the American list. The American 

 list also includes many very simple derivatives, such 

 as acetyl and benzoyl compounds, which swells its 

 bulk. One noticeable feature of the American list is 

 that it includes a large number of rarer inorganic 

 chemicals likely to be required for research purposes, 

 whilst the British list is largely made up of organic 

 chemicals. It is desirable that a new and more com- 

 plete edition of the latter should be issued as soon 

 a^ possible, and that requirements in inorganic, as 

 well as organic, chemicals should be kept in mind. 



The provision of a works laboratory is now 

 recognised as an essential part of the organisa- 

 tion of any large engineering firm. The equipment 

 will, of course, depend upon the kind of work 

 carried out by the firm. The laboratory at the Bed- 

 ford works of Messrs. W. IL Allen and Sons, Ltd., 

 forms the subject of an illustrated article in 

 Eni^ineering for January 13, and its equipment may 

 be taken as an excellent example of what is required 

 by a firm manufacturing a wide range of high-grade 

 mechanical engineering products. There is a main 

 mechanical testing-room, a chemical laboratory with 

 balance-room and stores, a recalescence room, a photo- 

 NO. 2727, VOL. 109] 



micrographic room, dark room, and office. The 

 mechanical testing equipment includes a Brinell hard- 

 ness machine, a Sankey autographic bending machine, 

 machines for repeated impact testing of the Eden- 

 Foster and Stanton types, an Izod impact machine, 

 a 30-ton Buckton machine with a Ewing extenso- 

 meter, and a Shore hardness testing machine. The 

 same room contains a number of machine tools for 

 the preparation of specimens. The chemical labora- 

 tory has also a very complete equipment ; the 

 recalescence furnace is a modification of the one in 

 use in the National Physical Laboratory. It is 

 perhaps unnecessary to add that this laboratory has 

 exercised a very effective control over the quality of 

 the firm's products. 



An introductory address to his lectures at University 

 College on waterways, harbours, and docks was 

 delivered by Dr. Brysson Cunningham on January 24. 

 The great value of the ocean as an international water- 

 way and the facilities it affords for traffic, with far 

 fewer difficulties than in the case of land routes, were 

 emphasised. Before the war railway construction in 

 England had cost something more than 50,000/. per mile, 

 including expenses of promotion, while in the United 

 States the cost averaged only about one-fifth of this 

 sum ; the outlay for track formation proper was about 

 5000Z. or 6ooo^ per mile. In both cases there is, in 

 addition, the expense of maintenance, whereas in a 

 waterway on the high seas there is neither cost of 

 construction nor of upkeep. This is true, though in 

 a lesser degree, of the rivers and inland waterways. 

 Dr. Cunningham also discussed ports, pointing 

 out that few modern ports have kept pace with 

 the requirements of the naval architect in regard to 

 ship design. Rational developments in shipbuilding 

 are impeded by lack of depth of water at the principal 

 ports and in the Suez Canal. The following table 

 shows the actual rate of expansion in the dimensions 

 of vessels in the mercantile marine during the past 

 forty years : — 



Average dimensions of the twenty largest steamships 

 in each of the years mentioned. 



Sir John Biles has claimed that it would be economical 

 to construct vessels up to 1000 ft. in length provided 

 it were possible to give them the appropriate draught 

 of 57 ft., but there are very few ports in the world 

 which could receive a vessel of this draught. Forty 

 feet is the extreme limit of draught which is available 

 at the present day for sea-going vessels. 



In the general article on "Agriculture at the British 

 .Association " in Nature of January 5, p. 25, it was 

 stated that "Mr. M. M. Monie gave an account of a 

 photographic survey of soils ... the method he pro- 

 poses, while of limited use by itself, should have a 

 useful place in soil-survey work." Mr. Monie writes 

 to say that his re«narks were "that a photographic 



