Chemistry and physics are experimental sciences; and those who are engaged in attempting to enlarge the boundaries of science by experiment are generally unwilling to publish speculations; for they have learned, by long experience, that it is unsafe to anticipate events. It is true, they must make certain theories and hypotheses. They must form some kind of mental picture of the relations between the phenomena which they are trying to investigate, else their experiments would be made at random, and without connection.

It cannot, of course, be stated with absolute certainty that no elements can combine with argon; but it appears at least improbable that any compounds will be formed.

One of the earliest questions asked by an intelligent child is: “What is this made of?” “What is that made of?” And the answer is generally more or less satisfactory. For example, if the question relates to butter, the reply may be, “From cream.” It may be explained, besides, that when cream is beaten up, or churned, the butter separates, leaving skim-milk behind. But the question has not been answered. The child may ask, “Was the butter in the milk before it was churned? or has it been made out of the milk by the churning?” Possibly the person to whom the question is addressed may know that the milk contained the butter in the state of fine globules, and that the process of churning breaks up the globules, and causes them to stick together. The original question has not really been answered; and indeed it is not an easy one to reply to. Precisely such questions suggested themselves to the people of old, and they led to many speculations.

Progress is made by trial and failure; the failures are generally a hundred times more numerous than the successes; yet they are usually left unchronicled. The reason is that the investigator feels that even though he has failed in achieving an expected result, some other more fortunate experimenter may succeed, and it is unwise to discourage his attempts.

There is a difference between discovery and invention. A discovery brings to light what existed before, but what was not known; an invention is the contrivance of something that did not exist before.

We have all heard of the puzzle given to Archimedes…. His finding that the crown was of gold was a discovery; but he invented the method of determining the density of solids. Indeed, discoverers must generally be inventors; though inventors are not necessarily discoverers.

Sir W. Ramsay has striven to show that radium is in process of transformation, that it contains a store of energy enormous but not inexhaustible. The transformation of radium then would produce a million times more heat than all known transformations; radium would wear itself out in 1,250 years; this is quite short, and you see that we are at least certain to have this point settled some hundreds of years from now. While waiting, our doubts remain.