ON A PIECE OF CHALK 55 



You may think this no very hopeful inquiry. You may not 

 unnaturally suppose that the attempt to solve such problems 

 as these can lead to no result, save that of entangling the 

 inquirer in vague speculations, incapable of refutation and 

 of verification. 5 



If such were really the case, I should have selected some 

 other subject than a "piece of chalk" for my discourse. 

 But, in truth, after much deliberation, I have been unable 

 to think of any topic which would so well enable me to 

 lead you to see how solid is the foundation upon which 10 

 some of the most startling conclusions of physical science 

 rest. 



A great chapter of the history of the world is written in 

 the chalk. Few pages in the history of man can be supported 

 by such an overwhelming mass of direct and indirect evi- 15 

 dence as that which testifies to the truth of the fragment of 

 the history of the globe, which I hope to enable you to read, 

 with your own eyes, to-night. 



Let me add, that few chapters of human history have a 

 more profound significance for ourselves. I weigh my words 20 

 well when I assert, that the man who should know the true 

 history of the bit of chalk which every carpenter carries about 

 in his breeches-pocket, though ignorant of all other history, 

 is likely, if he will think his knowledge out to its ultimate 

 results, to have a truer, and therefore a better, conception 25 

 of this wonderful universe, and of man's relation to it, than 

 the most learned student who is deep-read in the records of 

 humanity and ignorant of those of Nature. 



The language of the chalk is not hard to learn, not nearly 

 so hard as Latin, if you only want to get at the broad fea- 30 

 tures of the story it has to tell ; and I propose that we now 

 set to work to spell that story out together. 



We all know that if we "burn" chalk the result is quick- 

 lime. Chalk, in fact, is a compound of carbonic acid gas 



