be much more important. A phenomenon which cannot be explained by any known laws may indicate the interference of undiscovered natural forces. The ancients could not help perceiving that the general tendency of bodies downwards failed in the case of the loadstone, nor would the doctrine of essential lightness explain the exception, since the substance drawn upwards by the loadstone is a heavy metal. We now see that there was no breach in the perfect generality of the law of gravity, but that a new form of energy manifested itself in the loadstone for the first time.
Other sciences show us that laws of nature, rigorously true and exact, may be developed by those who are ignorant of more complex phenomena involved in their application. Newton’s comprehension of geometrical optics was sufficient to explain all the ordinary refractions and reflections of light. The simple laws of the bending of rays apply to all rays, whatever the character of the undulations composing them. Newton suspected the existence of other classes of phenomena when he spoke of rays as having sides; but it remained for later experimentalists to show that light is a transverse undulation, like the bending of a rod or cord.
Dalton’s atomic theory is doubtless true of all chemical compounds, and the essence of it is that the same compound will always be found to contain the same elements in the same definite proportions. Pure calcium carbonate contains 48 parts by weight of oxygen to 40 of calcium and 12 of carbon. But when careful analyses were made of a great many minerals, this law appeared to fail. What was unquestionably the same mineral, judging by its crystalline form and physical properties, would give varying proportions of its components, and would sometimes contain unusual elements which yet could not be set down as mere impurities. Dolomite, for instance, is a compound of the carbonates of magnesia and lime, but specimens from different places do not exhibit any fixed ratio between the lime and magnesia. Such facts could be reconciled with the laws of Dalton only by supposing the interference of a new law, that of Isomorphism.