122 Mr. W. H. Walenn's Remarks on the Atomic Theory. 



tions of the preceding year, the same result within 0*0022 of 

 the whole amount. It would scarcely be possible to find a better 

 example for showing the importance and significance of absolute 

 measures than the agreement of the two numbers, which are not 

 only based upon different observations, but even upon different 

 natural laws. 



The above determinations required for their execution less than 

 an hour and a half. If, moreover, as it seems, the accuracy at- 

 tainable is not inferior to that obtained by magnetic means, it 

 will in future be a question whether the voltaic determination of 

 T is not altogether to be preferred. It is undoubtedly so for 

 voltaic purposes. Adding to the two galvanometers a Weber's 

 terrestrial inductor, as in measuring inclinations, voltaic resist- 

 ances may be determined in absolute measure; and, for most 

 physical purposes for which no measurement of declination is 

 needed, we have an adequate magnetic voltaic observatory for 

 absolute measurements, in which, besides the needles used for 

 measuring the current, all fixed magnets are avoided. 



I will observe, in conclusion, that the construction of the in- 

 struments used for the above measurements, so far as it required 

 a mechanical workshop, w T as executed by Dr. Meyerstein. 



XVI. Remarks on the Atomic Theory. 

 By W. H. Walenn, F.C.S.* 



DR. WILLIAMSON has recently brought the atomic theory 

 again under the consideration of chemists ; and those who 

 adopt his views of the theory of combining proportions and of 

 multiple proportions (in short, his absolute interpretation of the 

 atomic theory) must also be prepared to give their entire and 

 unqualified assent to the following points : — 



1. In regard to the indivisibility of so-called "atoms:" — To 

 use the term " atom " in explaining a chemical combination is to 

 assume the truth of a theory which has for its basis the real ex- 

 istence of atoms ; and the word atom being derived from aTo/j,o$, 

 a word signifying " indivisible," leaves the atomists no alterna- 

 tive but to suppose that, by the operation of parting or division, 

 howsoever performed, upon a given mass of matter, a little mass 

 or lump of the material taken at last remains, beyond which no 

 division is possible. 



2. In regard to the existence of physical atoms : — Since Dr. 

 Williamson avows that in chemistry he acknowledges only one 

 atomic theory, namely that of Dalton, and ignores the efforts of 

 Lucretius (who was born B.C. 95) to develope the Epicurean 



* Communicated by the Author. 



