The variations in the market price of such commodities, therefore, can arise only from some accidental variation in the demand.

因此，此类商品市场价格的变化只能由需求的某些偶然变化引起。

The suddenness of the effect can be accounted for only by a cause which can operate suddenly, the accidental variations of the seasons.

效果的突然性只能由一个可以突然起作用的原因来解释， 即季节的偶然变化。