Edinburgh Geological Society. 555 
name of the “Silurian System.’ Now, the selection of this name by 
Murchison occurred exactly forty-eight years ago, and all the new 
and wider views which have since been opened up to us on the earlier 
ages of the history of the globe, and of the forms of life by which it 
was then inhabited—the whole of this knowledge has been gained 
within the half century of our existence as a society for the prosecu- 
tion of geological science. Within that period all the fathers of the 
science in our country have done their work, and have now, alas! all 
of them passed away. Buckland, and Conybeare, and Phillips, and 
De la Beche, and the still greater names of Murchison, and of Sedgwick, 
and of Lyell, are names which within the last few years have been 
added to the number of the illustrious dead. Let us stand back, 
gentlemen, from the picture which they have left, as artists sometimes 
stand back from the work of their own or of other hands, to get rid 
of details, and to grasp in one view the general effect. What is the 
general result of the facts which they discovered and of the principles 
which they have established as founded on those facts? And in order 
to answer this question, let us compare their work with the work of 
the half century which preceded them. That half century carries us 
back to the very dawn of geology as a science—to the time when 
men were still spending their energies in speculating on cosmical 
theories, instead of patiently collecting and investigating facts. And 
yet it cannot be said that their time was wasted. In a diamond neck- 
lace the whole value lies in the individual stones, and there is little or 
no intrinsic value in the strings or in the tissues which connect them. 
But this is not so in the jewellery of knowledge, in the brilliant 
acquisitions of the mind. Facts—bare facts—facts single and alone— 
are comparatively worthless. It is in their setting that all their value 
lies. It is in the connecting-links of thought, and in these alone, 
that they shine as guiding stars in the march of intellect—and take 
their final place in the firmament of knowledge. It was not for 
nothing, therefore, that in geology, as in other sciences, there was a 
time of wild speculation—of keen and rival theories—of Plutonists and 
Neptunists—which preceded the time of patient and laborious investi- 
gation. Without these golden threads of thought there would have been 
no possibility of stringing the pearls and precious stones which were dug 
out of the earth or recovered from the depths of ancient seas. But under 
the stimulus of rival theories, the digging and the diving have been 
vigorously prosecuted; whilst under the guidance of purely intel- 
lectual conceptions, the products of all this labour have been gradually 
set in that order which enables them to reflect and reveal the light. 
If any of us desire to see a signal illustration of the infinite value of 
speculation working on facts comparatively few and rare—a signal 
illustration of the power of the human mind, when well exercised, to 
penetrate by exercises of Reason—almost instinctive—into the secrets 
of Nature—let us study that most remarkable work, Dr. Playfair’s 
‘Explanation and Defence of the Huttonian Theory,” published in 
1803. I never look back to that book, remembering how little was 
then known of all that we now know, without rising from it with the. 
feeling that it is indeed an immortal work, and that we may well be 
proud of the two illustrious Scotsmen to whom we owe it. Apart 
