THE OPPORTUNITY OF THE AGRICULTURIST 689 



facts — it is at least a sound provisional working hypothesis. 

 How shall we attempt to demonstrate its truth ? Obviously, if 

 by bringing together lime and the gas which is given off when 

 limestone is dissolved in acid we can produce a material having 

 the properties of limestone, we shall have verified the hypothesis 

 and solved the problem as to the nature of limestone-stuff. 

 This turns out to be easy of accomplishment. On merely expos- 

 ing lime in a vessel full of the gas, it gains in weight just up 

 to the point required on the assumption that it is converted into 

 limestone-stuff; at the same time it acquires all the properties 

 of this material while losing those of lime. Sherlock Holmes 

 could do no more ! Or, arguing from the fact that lime is so 

 much more soluble than limestone, we may pass the gas into 

 a solution of lime in water : soon a solid falls out — a precipitate, 

 we call it — as we should expect would be the case if the gas 

 were to unite with the lime in solution. Having carried out 

 the experiment on a scale such that 2 or 3 grams of the product 

 are available, it is possible to ascertain what weight of lime it 

 yields when burnt and what amount of gas is given off when 

 it is dissolved in acid — and so to characterise it as chalk-stuff, 1 

 for the mere appearance of the precipitate proves nothing. 



And proceeding in this way, discovery follows discovery ; 

 even carelessness sometimes has its place. Thus, when through 

 an oversight or forgetfulness, perhaps, the gas is passed into the 

 lime-water during some considerable time, the precipitate seems 

 to lessen instead of increasing in amount, as if it were soluble 

 in presence of the gas. Does not such an observation serve to 

 recall the fact that natural water sometimes contains an inex- 



1 Objection has more than once been taken to the use of expressions such as 

 "chalk- stuff 1 ' or "limestone-stuff" and " chalk-" or "limestone-stuff" gas : never- 

 theless I continue to use them and do so advisedly. Chalk and limestone are not 

 definite substances but species of natural material which, if destroyed, cannot be 

 reproduced : the names have a definite geological connotation but no chemical 

 meaning. The varieties of limestone are composed of a definite substance in 

 greater or less proportion : to call this substance from the outset by its recognised 

 scientific name, when the game of an inquiry into its nature is being played, is 

 simply to give away the game entirely from the outset and make it a worthless 

 one to play from the point of view from which alone the game is worth playing — as 

 a means of gaining knowledge of method. Let me urge that provisional names 

 must be used throughout every inquiry. " Stuff" is an honest old English word of 

 which far too little use is now made. Probably if I had called the gas Gypsogen, 

 little objection would have been raised : but it is difficult to be rational in these 

 modern times. 



