58 OBSER VA TION NECESSAR Y. 



of the identity of lightning and electricity it was 

 sneered at, and people asked, ' Of what use is it ?' 

 to which his apt reply was 'What is the use of a 

 child ? It may become a man !' Again, many 

 before Galileo had seen a suspended weight swing 

 before their eyes with a measured beat, but he was 

 the first to detect the value of the fact. One of the 

 vergers in the cathedral of Pisa, after replenishing 

 with oil a lamp which hung from the roof, left it 

 swinging to and fro, and Galileo, then a youth of only 

 eighteen, noting it attentively, conceived the idea of 

 applying it to the measurement of time. Fifty years 

 of study and labour, however, elapsed before he com- 

 pleted the invention of his pendulum, an invention the 

 importance of which can hardly be overvalued. 



'Again, while Captain (afterwards Sir Samuel) 

 Brown was occupied in studying the construction of 

 bridges, with the view of contriving one of a cheap 

 description to be thrown across the Tweed, near 

 which he lived, he was walking in his garden one 

 dewy autumn morning, when he saw a tiny spider's- 

 net suspended across his path. The idea imme- 

 diately occurred to him that a bridge of iron ropes or 

 chains might be constructed in like manner, and the 

 result was the invention of his suspension bridge.' 



I can give you also another story, teaching us 

 not to be satisfied until we know, if possible, the 

 object and the use of even the smallest thing in any 

 department of natural history, which we may be 

 studying. It is the story of another discovery, as 

 wonderful as any ever made, and which has brought 

 the greatest blessings to the world, and has been the 



