January ii, 1912J 



NATURE 



300 



eight to ten days, the ruling diamond (which must be 

 selected and mounted with great care) has to trace a 

 furrow several miles long on a surface as hard as steel, 



ind often breaks down when the grating is half finished. 



I he work cannot be continued with a new diamond, and 

 must be rejected and a new grating begun. 



Thirdly, the slightest yielding or lost motion in any of 

 rlie parts — screw, nut, carriage, or grating — or of the 

 mechanism for moving the ruling diamond, is at once 

 - \ idi-nct d b\ a kut- -ponding defect in the grating. When, 

 ;ift' r w ' kv, i.r mhit times months, of preparation all seems 

 in rtadiius> lo bt^iii ruling, the diamond point gives way, 



ind as much time may have to be spent in trjing out a 



I'W diamond. 



When the accumulation of difficulties seems to be in- 

 surmountable, a perfect grating is produced, the problem 



- considered solved, and the event celebrated with much 

 !• joicing, only to find the next trial a failure. In fact, 



nore time has been lost through such premature exhibi- 

 rions of docility than in all the frank declarations of 

 -rubborn opposition ! 



One comes to regard the machine as having a person- 

 ility — I had almost said a feminine personality — requiring 

 amouring, coaxing, cajoling, even threatening! But 

 iially one realises that the personality is that of an alert 

 nd skilful player in an intricate but ^ c-:-. -^ game 

 ho will take immediate advantage of th - of his 



pponent, w-ho " springs " the most d g sur- 



rises, who never leaves any result to chance, but who 



• vertheless plays fair, in strict accordance with the rules 

 f the game. These rules he knows, and makes no allow- 



.r\<x if you do not. When you learn them, and play 

 accordingly, the game progresses as it should. 

 As an illust-ation of \h<- nuasure of success attained in 

 lis work, I would direct attention to a recent comparison 

 V Messrs. Gale and I^emon of tf»e performance of a 

 rating of 6J-inch ruled sufface w^ith that of the echek>n, 

 he Perot and Fabry interferometer, ir. The test object 



- the green radiation from incandescent mercury vapour. 

 he spectrum of •-■ ' tion had been supposed a simple 

 ne until the i '-x showed it to be made up of 

 ve or more c<. , The whole group occupies a 

 :>ace about one-fifteenth of that which separates the 



>dium lines. 



- six components, while the 



its give from six to nine, 



■><' <'i ''■ - it a distance apart of only 



'5<* of : n the sodium lines, and 



iiese are so . , a the grating that it would 



• possible to distinguish doublets of one-half to one-third 

 his value, so that tf»e actual resolving power is inxn 



■0,000 to 400,000 — of the same order, thtrefore, as that 



: the echelon. 



It may well be asked, why is it necessary- to go any 



.rther? The s,ime question mas put some twentv vean» 



go when Rowland first astonished the scientific world 



ith resolving powers of 100,000, and it was his belief 



at the width of the spectral lines themselves w-as so 



'^t that no furtt>er "resolution" was possible. But it 



)S been abundantly shown that this estimate proved in 



rror. and we now know that there are problem* the sohi- 



• ion of whi<ii depends on the use of resolving powers of at 



:• ast a million, and others are in sight which will re<|uire 



II million for their accurate solution, and it is safe to 



v Th.1t the supply will meet the demand. 



to our comparison of die telescope and die 



: while the progress of «nvie<itigatioa of the 



rse will be ever furthered " .>«d site and 



wer of the telescope, : y seriouslT 



the turbulenoe of die ;....... .....eji of atmo- 



gh which the obserratioRs vmaast be made. Bat 



corrcsiomUng limit to the effectrre power of 



and die solution of the corresponding 



the subatomic structures and motions of this 



. roscopic univenM maf be confidenthe awaited in the 



iture. 



me«Mges we r-^^v- (,-r^ the depth of die stellar 

 •irmament or from t' arcs of our laboratories, - 



«s>me they in a milli. <«cond or in lnindr«ds of 



light-yeans, are faithful r«^Ard-i of evenfci of prtilound 



NO. 2202. vni . 88] 



<• to the race. They come to us in OT**^ — '" * 

 ve are only beginning to understand. 

 I ;ur present duty is to make it po s sibl e to receive and 

 to record mch messages. When the time ooaet for a 

 Kepler and a Xcwtoa to translate tfaem w« may eaipect 

 aiarvels which will require die utrooat powers «€ <Mir 

 intellect to grasp 



B^ 



THE CARBOMSATION OF COAL. 

 I. 

 EFORE it is possible to explain the highly twm pIeK 

 actions taking place in the destrucdve dt<ti1la«iwi 

 of coal, it is important to have «ome definite idea of 

 the nature of the raw material with which we have to 

 deal ; and although many attempts have been made to 

 gain an insight into the composition of ooaL, the wide 

 variations in its characteristics, At dMhwities altnirfng 

 any attempt to separate its const it uents, and the case 

 with which the products of its decomposition undergo 

 secondary changes at the temperatures employed in break* 

 ing it up, have prevented any very satisfactory solation 

 of the problem being arrived at. 



The one thing generally admitted is that coal is the 

 fossil remains of a ve^getation that flourished in the car* 

 boniferous period of the worM^s history, and that it ha* 

 passed through successive stages of checked decay: the 

 action of time, temperature, and pressure, generally out 

 of contact with air, resulting in the oooversion of these 

 into the tertiary coals (sudi as brown coals or lignites), 

 and probably by a continuance of the action yielding 

 eventually the true coaL 



All the plants of which we have fossilised reooid in 

 our coal measures ooosisted of sei^^ and reeds, tree 

 ferns, club mosses or lyoopodia, and trees akin to the 

 pine ; but in those prehistoric days the conditions of flrowdi 

 — warmth, moisture, and carbon dioxide — were sudk that 

 these plants grew with a succulent fre«doai and rap«<fity 

 unknown in latter days, and which rradered their tassoes 



an easy •. '^ ''fcay and fermentation — actions which 



left only resistant unchai^HL The wwlc of 



Morris, C . Flemii^ and Huxley has shown us 



that tl^ bituminous matter in coal is lar^y derived from 

 the spores of fossi! mosses akin to the hxopodia. If wt 

 take the club mosses of to-day, we find their spores ^ve 

 us the body known as lyoopodium — a substance so resino— 

 in its nature that it resists the action of wMer, and is 

 u.«ed to coat pills, while the same ressMms cfcaracteristMS 

 render it so inflammable that a Gttle Mown thn a^ ri i • 

 flame provides the theatrical world widi its aartWdal 

 lightning. Spores of this character, from the giant grMith* 

 of the carboniferous period, tc^^lier with the more resino MS 

 portion of plants akin to die pine, am the «ib«NMnei 

 ' \e best resisted the actions taking pboe iatimg 

 hat have elapsed in die fai mrti on of cemL 



>,,„ ^ with the 0ire of the otiginal plants, we find 



two well-defined bodies— cellulose, as r e p reue nted b» cotton 

 fibre, and lignose, as represented by fute fibre. In the 

 former, the percentage of carbon is 44, in the latter 47 

 — each givii^ distinctive reactions with dilute acids at 

 70* C, with aniNn sulphate, widi SchnfcM sohrtion, and 

 with mixtures of sulphiRic and nitric acids., la ifce celMar 

 tissue, we find starch; and besides Aew bodies, tkcre 

 are present the extractive wnd mamni msnert of the ssp. 



Among the extractive matltr we find ^tm» — mtA as 

 those exuding from the aeita* and cherry, but also prwwt 

 in the juice of many plants^ mwcilaipe, vqpe tsble ^ jeli y 

 (which gives many juices dMsr g wm of ^gt*Mi nMgg^ 

 resins, essential oils, and other niH difincd boSes. With 

 some forms of ve^getation, the eaaeMial oils anlui^a 

 tion and form resins; and tbfe8(>, htimg mayt ws** 

 change, accumulate in masses of decaying vt^ table ^ 

 so that largt* quantities of them are found m Qgnite beds 

 in a fossilised, but little chai^jed. state. 



The cha»g«e« in the carbohvdrates and exunttiv* oMMtrt 

 depend Urgdv upon the condMoaa «f decay. Givta HMis> 

 ture aiid air, thev beonme converted into carbon d B o oii d i 

 and water ; dieck the decay by cnttinc off ft«e aocoas of 

 1 FraM a <vMn» M C»mar L«or««k «*«• m riM K>i >d l ^^tm* ^ K^t* i« 

 »<mwtb«raw< l Viu.n » i ) i . tftv >y PkJ: V»n" 



to 



■ ▼ iVVMI B^ SjCMV^ 



