762 THE POPULAR SCIENCE MONTHLY. 



cases prove little or nothing, except the weakness, and possibly the in- 

 sincerity, of the Legislature, But if an act comes largely into opera- 

 tion it is practically irrevocable. Parliament can not say simply " as 

 you were," and proceed to a new and more hopeful experiment. A 

 social humpty-dumpty can not be set up again just as it was before 

 even by the Queen's men. The vested interests created are usually 

 too formidable to be put aside, and too expensive to be bought up. A 

 good many years, say seven, or ten at the least, are needed to develop 

 properly any important legislative experiment, so that the same gener- 

 ation of statesmen would not have more than three or four opportu- 

 nities of experiment in the same subject during the longest political 

 career. If we divide up the country, and try one experiment on one 

 town or county, and another on another, there is a possibility of mak- . 

 ing an almost unlimited number of valid trials within ten or twenty 

 years. But, apart from this consideration, a general legislative change 

 is not a true experiment at all, because it affords no clear means of 

 distinguishing its effects from the general resultant of social and in- 

 dustrial progress. Statistical facts are usually numerical or quantita- 

 tive in character, so that, if many causal agencies are in operation at 

 the same time, their effects are simply added together algebraically, 

 and are inextricably merged into a general total. Thus, the total num- 

 bers receiving poor-law relief, or the numbers apprehended in the king- 

 dom for drunkenness, are numerical results affected by the oscillations 

 of trade, by the character of the seasons, the value of gold, etc., etc., 

 as well as by the acts of the Legislature. To make a valid experiment 

 we must have a certain thing subject to certain constant conditions, 

 and we must introduce a single definite change of condition, which 

 will then be probably the cause of whatever phenomenon follows. It 

 is possible, indeed, to experiment upon an object of varying condi- 

 tions, provided we can find two objects which vary similarly ; we then 

 operate upon the one, and observe how it subsequently differs from the 

 other. We need, in fact, what the chemists call a " blind experiment." 

 Suppose, for instance, that an agricultural chemist or a scientific farmer 

 wished to ascertain the effect of a new kind of manure ; would it be 

 rational for him to spread the manure over all his available land? 

 Would it not then be doubtful whether the increase or decrease of 

 yield were due to the manure or to the character of the seasons ? In 

 this case his neighbors' crops might, to some extent, furnish the blind 

 experiment, showing what had been the ordinary yield. But, of 

 course, the obvious mode of procedure is to spread the new manure 

 over a part only of each experimental field, so that the difference of 

 the crops on the different patches brings out, in the most unquestion- 

 able way, the effect of the manure. Not only is the smaller experi- 

 ment, in a logical point of view, far better than the larger one, but it 

 is possible to try many concurrent small experiments upon a farm of 

 moderate extent. 



