THE OPPORTUNITY OF THE AGRICULTURIST 687 



of finding out, what will you answer ? I fancy some one says : 

 " Make sure that the water really is all expelled, weigh the 

 lime, then pour a known quantity of water upon it, let it 

 slake and weigh the dry powder. Don't work in a bricklayer's 

 empirical fashion but be scientific ; control all your actions by 

 weighing and measuring." Good ! Such advice is worth follow- 

 ing. With very little trouble we find that although some of the 

 water is driven off as steam, much of it remains with the lime — 

 the weight increasing by about one-third. It is thus discovered 

 that lime has a great affection for water; but the union is 

 marked by considerable display of temper, by heat. Was the 

 lime in the limestone? If so, how was its affection for water 

 masked ? What happened in the burning to confer so powerful 

 a thirst upon it ? Let us again be scientific and watch the 

 limestone burning with the aid of the balance — the man in 

 charge of the limekiln tells us that the lime produced always 

 weighs less than the limestone which is burnt. Taking whiten- 

 ing, as being the cleanest form of limestone procurable, on 

 burning it in a crucible in a gas muffle furnace until it no longer 

 changes in weight, it loses slightly less than 44 per cent., leaving 

 about 56 per cent, of lime; however often the experiment be 

 repeated with the whitening, the result is always practically the 

 same, though different limestones give different results according 

 as they contain more or less clay or grit. Assuming that the lime 

 is precontained in the limestone, it would seem that, unless it be 

 in some way destroyed, about 43-44 per cent, of the whitening 

 is driven off into thin air — since there is no visible smoke such 

 as would be noticeable if a condensible substance were expelled. 



I have chosen these two simple examples as illustrations of 

 the way in which with a little care and consideration you can 

 make use of ordinary commonplace but suggestive occurrences 

 as arguments in devising experiments, with the object of solving 

 problems relating to common objects and common phenomena ; 

 our scientific method of working is nothing but common sense 

 writ large systematically applied to practice. 



But this by way of parenthesis. We are only beginning to 

 understand limestone. Let us look further into its doings; it 

 seems to be full of interest. 



In limestone districts, where hard water is used, people 

 know quite well that there is often a deposit from such water 

 when it is kept in water-bottles in hot weather and that 



