16 GENERAL VIEW AND BASIS OF SCIENTIFIC RESEARCH. 



temperature, such as may now prevail in other parts of the 

 universe, a great number of new compounds would be 

 capable of existing. We already possess evidence of this in 

 the fact that under the influence of great pressure or a low 

 temperature, new compounds, such as the various cryohy- 

 drates, also ammonium, and hydrate of chlorine, may be 

 obtained, and such additional bodies would add to the 

 number of possible compounds. But the few additional 

 instances of this kind with which we are at present ac- 

 quainted also conform to, and therefore confirm, the law 

 that elementary bodies only unite in certain definite 

 atomic proportions by weight, and do not unite in the 

 proportions of fractions of their atomic weights to form an 

 unlimited number of compounds. The spectroscope has 

 shown us that various substances in the elementary state, 

 and probably some new elementary substances, exist in 

 the more intensely heated heavenly bodies ; but neither it 

 nor any other instrument has yet supplied us with evi- 

 dence of the existence of new compounds in the colder 

 parts of the universe. Not only does it appear highly 

 improbable that an unlimited variety of collocations of 

 different atoms, united to form different substances, can 

 exist ; but many combinations and arrangements of forces 

 are incompatible, and cannot co-exist. From these con- 

 siderations, therefore, there is probably a limit to the 

 number of natural existences, whether of forces, sub- 

 stances, or their phenomena, within reach of our observa- 

 tion, and consequently also to the amount of possible 

 knowledge respecting them. The number of laws also 

 which govern a finite number of substances or forces 

 must themselves be finite. There are also statements in 

 logic which are contradictory ; mathematical quantities 

 which are impossible ; geometrical conditions which are in- 

 conceivable ; mechanical arrangements which are self- 



