552 THE PRINCIPLES OF SCIENCE. [CHAP. 



of physical science. Only a few instances of each class 

 can be given here. 



Empirical Measurements. 



Under the first head of purely empirical measurements, 

 which have not been brought under any theoretical system, 

 may be placed the great bulk of quantitative facts recorded 

 by scientific observers. The tables of numerical results 

 which abound in books on chemistry and physics, the huge 

 quartos containing the observations of public observatories, 

 the multitudinous tables of meteorological observations, 

 which are continually being published, the more abstruse 

 results concerning terrestrial magnetism such results of 

 measurement, for the most part, remain empirical, either 

 because theory is defective, or the labour of calculation 

 and comparison is too formidable. In the Greenwich 

 Observatory, indeed, the salutary practice has been main- 

 tained by the present Astronomer Royal, of always redu- 

 cing the observations, and comparing them with the theories 

 of the several bodies. The divergences from theory thus 

 afford material for the discovery of errors or of new phe- 

 nomena ; in short, the observations have been turned to 

 the use for which they were intended. But it is to be 

 feared that other establishments are too often engaged in 

 merely recording numbers of which no real use is made, 

 because the labour of reduction and comparison with 

 theory is too great for private inquirers to undertake. In 

 meteorology, especially, great waste of labour and money 

 is taking place, only a small fraction of the results recorded 

 being ever used for the advancement of the science. For 

 one meteorologist like Quetelet, Dove, or Baxendell, who 

 devotes himself to the truly useful labour of reducing other 

 people's observations, there are hundreds who labour under 

 the delusion that they are advancing science by loading 

 our book-shelves with numerical tables. It is to be feared, 

 in like manner, that almost the whole bulk of statistical 

 numbers, whether commercial, vital, or moral, is of little 

 scientific value. Purely empirical measurements may 

 have a direct practical value, as when tables of the specific 

 gravity, or strength of materials, assist the engineer ; the 

 specific gravities of mixtures of water with acids, alcohols, 



