This is generally assumed to be the case in mathematical problems, but the assumption is admissible only in rough work, or if the temperature difference is small.
The first paper of Maxwell's in which an attempt at an admissible physical theory of electromagnetism was made was communicated to the Royal Society in 1867.
When two or more modes of accounting for a phenomena are equally admissible as not directly contradicted by known phenomena, it seems to Epicurus almost a return to the old mythological habit of mind when a savant asserts that the real cause is one and only one.
It is still admissible, however, to doubt whether the hateful consequence does not follow consistently from the theory laid down.
As to the nature of the chief factors concerned in the two revolutions in the vegetable kingdom, if it is admissible to use so strong a term, only a guess can be hazarded.