86 LIGHT SCIENCE FOR LEISURE HOURS. 



on in the requirements of the country. Year by year 

 Britain has a larger population, and the average 

 requirements of each member of the population are 

 also increasing. But we have seen that the increase 

 of her population is necessarily limited ; and although 

 the increase of the requirements of her people may not 

 be (strictly speaking) limited, yet it is manifest that,, 

 inasmuch as that increase depends on causes which are 

 themselves approaching a limit, its rate must, after a 

 time, continually diminish. Let it be understood that, 

 when I speak of the requirements of the population,. 

 I do not mean only what they must obtain from other 

 countries. The commerce of a country is the expres- 

 sion of the activity with which the nation is ' earning 

 its living,' so to speak, and in a given population there 

 is a limit to what is necessary for this purpose, precisely 

 as there is a limit to the sum which an individual 

 person in any given state of life requires for the main- 

 tenance of a given family. Indeed, although such 

 comparisons are not always safe, we may in this case 

 compare what may be called the commercial require- 

 ments of the nation with the requirements of the head 

 of the family, a merchant suppose. There are no 

 limits to the degree of wealth which a merchant may 

 desire to gain, but unquestionably there are limits to the 

 income necessary to maintain his house and family and 

 mercantile position. Supposing he were extending his 

 gains far beyond his actual requirements, it would by 

 no means imply his approaching ruin that there was 

 a demonstrable limit to this extension. And in like 



