66o THE POPULAR SCIENCE MONTHLY. 



concentrated by means of a lens ? There has been received from it 

 mental, artistic, and moral culture. The invention has opened up a 

 new field of investigation and research to the labor of the chemist and 

 to the student of nature. From the first announcement to the world, 

 to the present hour, a host of inventors have been engaged in perfect- 

 ing and improving the art, enlarging the field of its applications, and 

 studying the laws of nature upon which it rests. The boundaries of 

 human knowledge, in more than one department of physics, have been 

 greatly extended in these efforts. Astronomy has received important 

 aid from it, and by its help we get not merely jiictures of what exists 

 in the heavenly regions, but records of what is there talcing place. 



This art has even come to play an important part in the adminis- 

 tration of justice and in the protection of the community against crime. 

 By its aid criminals are detected, watched, and convicted. Forgeries 

 are proved or disproved by its use. It finds an important place in the 

 ordinary business of commerce and the mechanic arts. By its aid, 

 copies or representations of all valuable works of art are placed with- 

 in the reach of multitudes who, otherwise, would know nothing of them 

 or know them only through inadequate verbal description. The im- 

 provement of the public taste in relation to art, by the knowledge of 

 works of art which has been thus diffused, has been very great. 



Does any one doubt that this extension and this sj)read of knowl- 

 edge of the works of art must tend to the improvement of man's moral 

 nature ? Can it be doubted that the social affections are quickened by 

 the preservation of the features of friends and the interchange among 

 friends and families of pictures of those who make up the family cir- 

 cle ? Will not a boy, absent from home, feel the influence of home 

 more strongly when he looks upon the faces of parents or sisters, than 

 he would if he could not thus bring them into his presence? 



But all these benefits which the world reaps from photography have 

 come to us from inventions. It is not the fruit so much of genius, as 

 of that patient labor and research which is winning from Nature, day 

 by day, secrets far more valuable to man than all her hidden treasures 

 of gold and silver. 



Within the memory of men not very old, a new power has, by the 

 genius of inventors, been trained into the service of man. This power 

 is electricity. It has always, as we now know, been present in many 

 of the phenomena of nature, exhibiting itself most strikingly in the 

 lightnings of the thunder-storm, revealing, as man believed, the pres- 

 ence of a mysterious power which might be destructive, but which 

 never could be useful to man. 



A trifling incident revealed to an observing man in Italy the fact 

 that, when two metals and the leg of a frog were made to touch, the 

 muscles of the leg were contracted. This was a little more than a hun- 

 dred years ago. This led to the invention of the galvanic battery, an 

 instrument by which man was enabled to generate electricity for his 



