February 25, 191 5] 



NATURE 



701 



should be held at an early date to formulate such 

 a scheme. Even if to-morrow the whole of the 

 available chemical force set to work on some 

 organised plan, it would not be any too soon to 

 g-et the necessary information together for the 

 use of the existing- works and the new works 

 when they are started. 



The urgency of this action is further shown by 

 a resolution passed by an important meeting held 

 in Manchester on February i6, which was pre- 

 sided over by Sir Chas. Macara.. The resolution, 

 which was carried unanimously, stated : " That in 

 the opinion of this meeting the Government would 

 do well to organise immediately the present 

 chemical talent in the country with a view to 

 chemical research being undertaken for, and on 

 behalf of, all manufacturers interested, and that 

 the services of these experts should be available 

 for all desirous of availing themselves thereof." 



The adoption of such a plan for bringing the 

 educational institutions more closely into touch 

 with the industries would in all probabilit\' mark 

 the beginning of a new era in which both would 

 benefit. The more intimate association of pro- 

 fessors of chemistr\- with chemical industry would 

 introduce into the works that higher ideal and 

 broader scientific spirit upon which successful 

 research and development depend; whilst the 

 schools would benefit by the great incentive of 

 practical reality. 



The Parliamentary Debate. 



Since the above was written, the important de- 

 bate in the House of Commons on Monday, Febru- 

 ary 22, has advanced the matter another stage. The 

 criticisms offered by various speakers raised few 

 novel points, and the general tone of the debate 

 was, on the whole, favourable to the Government 

 scheme. Several speakers, including Sir Philip 

 Magnus, expressed the opinion that the grant of 

 ioo,oooZ. for research work was totally inade- 

 quate. Mr. A. Chamberlain and others emphasised 

 the great difficulties the undertaking would have 

 to face on the conclusion of the war, and many 

 speakers acknowledged that the question of the 

 manufacture of dyes was of such a special char- 

 acter as to warrant quite exceptional treatment. 



Mr. Runciman, speaking on behalf of the 

 Government, made the interesting announcement 

 that upwards of 400,000^ has already been sub- 

 scribed towards the capital of the new company, 

 and further stated that the signing of the five 

 years' agreement was not an essential condition 

 of subscribing capital, but that priority of supply 

 would be given to those who had given the under- 

 taking. His concluding remarks may be quoted : 

 " I am surprised that anyone should suggest that 

 we have not adequate chemical knowledge in this 

 countrj'. We have sufficient first-class men, but 

 we lack an adequate number of second-class 

 chemists, which we shall not produce if they are 

 only paid 3L a week. 



" Even if this were only an emergency scheme 

 the million pounds promised by the Government 



NO. 2^6^, VOL. Q4l 



would be well spent. A single month of unem- 

 ployment in the textile trade would mop up more 

 than that of our national money. It is the dis- 

 advantage of all practical schemes that they are 

 full of compromises, but no step has been taken 

 without a practical reason." 



Walter M. Gasdnbb. 



OX COLOUR SENSITISED PLATES.' 



II. — Their Applications. Panchromatic Plates. 

 Testing Dyes, etc. 



The commercial " ortho-" or " iso-chromatic " 

 plates, which are specially sensitised for green, 

 besides their obvious uses for scientific purposes 

 in which red sensitiveness is not necessary, are 

 of especial use in the photography of coloured 

 objects where an improved result, as compared 

 with an ordinary plate, is desired, rather than; a 

 full correction. As the unassisted eye is not . a 

 very keen critic of the relative brightnesses of 

 different colours, especially when they are not in 

 juxtaposition, such an improvement is often all 

 that is necessary. The deficient sensitiveness to 

 red causes a pure red to be represented as if it 

 were black. But almost all colours in nature and 

 most artificial colours are not pure, and so far 

 as a red contained any green or white, that is 

 so far as it reflected any other light whatever in 

 addition to the pure red, except pure blue, then 

 the rendering of the red would be improved. But 

 this fact as to most natural colours being mixed 

 is also a disadvantage, for all coloured objects, 

 so far as they reflect any red, will suffer because 

 of the want of red sensitiveness of these plates. 



Plates are made sf>ecially sensitised to red and 

 called red and yellow sensitive, and practically 

 all that has been said with regard to green sen- 

 sitised plates, both now and in the previous article, 

 applies to these, only that the deficiency here is 

 green instead of red. 



By the use of more than one sensitiser, plates 

 may be sensitised to both green and red, and the 

 early panchromatic plates were of this tjpe. They 

 had three maxima of sensitiveness, one in the blue 

 due to the plate (that is, the silver bromide) not 

 specially sensitised, and one in the green and one 

 in the red due to the two sensitisers. Such plates 

 may be regarded as being as much of an improve- 

 ment on " orthochromatic " plates as these are on 

 ordinary plates, but the sensitiveness is uneven, 

 and they consequently suffer as already described. 

 By the careful selection and combination of sensi- 

 tisers this unevenness has been very largely over- 

 come in the panchromatic plates of the present 

 day. Excessive blue sensitiveness of course re- 

 mains, but this is easilv obviated bv a pure vellow 

 filter. 



The three illustrations (Fig. 2, a, b, c) show the 

 effects of various colours by the use of ordinary, 

 orthochromatic, and panchromatic plates, respec- 

 tively. The colour filter used with the ortho- 

 chromatic plate might with advantage have been 



1 Continued ftxKP p. 677. 



