TRANSACTIONS OF THE SECTIONS. 29 



very passing notice, and were not unfairly considered to be unnecessary complica- 

 tions of tlie theory. It was left for time to accumidate facts, for wliicli Dalton's 

 theory supplied no explanation of any kind, and these were at first neglected ; but 

 as their number increased, their explanation was evaded by the invention of names 

 intended to group together facts supposed to be dependent on similar causes. Such 

 names as catalysis, allotropy, and the like, really explain nothing; they are little 

 better than scientific lumber-rooms, in which unexplained facts are stowed away 

 until it suits our knowledge or oiu' convenience to classify and exjilain them. I 

 am far from asserting that this mode of grouping facts supposed to have something 

 in common, has not its advantages, provided only it be distinctly imderstood that 

 it is the grouping of ignorance. The risk lies in the name bemg accepted as au 

 explanation, and inquiry being thereby retarded — and something of this sort has 

 indeed occurred ; for though these facts were admitted to be beyond the scope of 

 the atomic theory, they were quietly sat aside ; things went on as they were before, 

 and it was not till the introduction of the theory of atomicity, which shows itself 

 in every chemical fact, that the doubts which had been long gathering in the 

 minds of all thoughtful chemists, found distinct expression. I do not on the pre- 

 sent occasion propose to discuss in detail the effect which the introduction of this 

 view has had upon chemical theory, further than to remark that it renders it 

 necessary either to abandon altogether the atomic theory of Dalton, or to introduce 

 into it such modifications as fundamentally alter its entire character, and make it 

 substantialh' a new theory. The former is an alternative which some chemists 

 will be gTeatly disinclined to adopt. They will not willingly abandon a theory 

 which has admittedly done admirable service, which at its first introduction estab- 

 lished order and regularity where confusion and disorder previously reigned 

 supreme, and under whose influence the science has attained its present goodly 

 proportions. Others again may be of opinion that the atomic theory has done its 

 work, and in the future is less likely to act as an assistance than as a hindrance to 

 progress, by forcing us to consider all facts in its particular light, and causing us to 

 overlook relations which might be at once detected by an unbiassed mind. 



This latter opinion has been very strongly expressed by Sir Benjamin Brodie, 

 and in the Calculus of Chemical Operations, which he has recently made public, 

 we have the first systematic attempt which has been made to express the consti- 

 tution of chemical compounds by a method in which the idea of an atom has no 

 place. As this is the most important chemical doctrine which has been put 

 forward for many years, and must, if accepted, materiallj^ alter our present ■\iews, 

 I shall venture to consider it in some detail, premising, however, that as only the 

 first part of the investigation has yet been made public, any opinion I may now 

 express regarding it may be liable to modification when the entire investigation is 

 published. 



Sir B. Brodie, as has been already observed, discards altogether the idea of an 

 atom, and compares with one another the weights of diflerent substances in the 

 gaseous state which are capable at the standard temperature and pressure of filling 

 a unit of space, which is the bulk of 1000 cubic centimetres. If we consider this 

 space to be empty, and fill it with hydrogen, a chemical operation is performed 

 which is represented by the symbol a, expressing the fact that the weight so intro- 

 duced is chemically indivisible. If now in place of hydrogen oxygen be introduced, 

 the unit of space is filled by a quantity sixteen limes as great, but this weight is 

 not indivisible, as is at once apparent if we notice what happens when oxygen is 

 introduced into the unit of space ah'eady fiUed with hydrogen. In that case a 

 second operation is performed on it, in which a weight eight times as great as that 

 of the hydrogen is introduced, and water is the result. The quantity of oxygen 

 which fills the unit of space must therefore be regarded as divisible," and this is 

 expressed by assigning to it the symbol ^^,, indicating the fact that two identical 

 operations are required to fill the unit of space with oxygen. By the same line of 

 argument it is concluded that sulphur, selenium, &c., miist be similarly constituted, 

 and they are accordingly represented respectively by 6.,, X,, &c. So far it will be 

 observed that the system is merely a modification of that at present used by che- 

 mists for expressing the laws of gaseous combination, excepting that all substances, 

 compounds as well as elements, are referred to the unit of space, while, according 



