1818.] History of Dr. Brewster's Kaleidoscope. 61 



in the position of symmetry, and put in motion either by a rotatory 

 movement, or by their own gravity, or by both combined. The 

 second form of the instrument, described in the specification, 

 is when the tube containing the reflectors is placed in a second 

 tube, at the end of which is a convex lens which introduces into 

 the picture objects of all magnitudes, and at every distance, as 

 has been already described. 



After the patent was signed, and the instruments in a state of 

 forwardness, the gentleman who was employed to manufacture 

 them under the patent, carried a kaleidoscope to show to the 

 principal London opticians, for the purpose of taking orders 

 from them. These gentlemen naturally made one for their own 

 use, and for the amusement of their friends ; and the character 

 of the instrument being thus made public, the tinmen and glaziers 

 began to manufacture the detached parts of it, in order to evade 

 the patent ; while others manufactured and sold the instrument 

 complete, without being aware that the exclusive property of it 

 had been secured by a patent. 



In this way the invasion of the patent, right became general 

 among that class of individuals against whom the law is seldom 

 enforced but in its terrors. Some workmen of a higher class 

 were encouraged to piracy by this universal opposition to the 

 patent ; but none of the respectable London opticians would 

 yield to the clamours of their customers, to encroach upon the 

 rights of an inventor, to whom they were at least indebted for a 

 new and a lucrative article of trade. 



In order to justify these piratical proceedings, it became 

 necessary to search out some combinations of plain mirrors, 

 which might be supposed to have some resemblance to Dr. 

 Brewster's instrument ; and it would have been strange indeed 

 if some theorem or experiment had not been discovered, which 

 could have been used to impose upon the great crowd who are 

 entirely ignorant of the principles and construction of optical 

 instruments. There never was a popular invention which the 

 labours of envious individuals did not attempt to trace to some 

 remote period ; and in the present case so many persons had 

 hazarded their fortunes and their characters, that it became 

 necessary to lay hold of something which could be construed into 

 an anticipation of the kaleidoscope. 



The first supposed anticipation of the kaleidoscope was found 

 in Prop. XIII. and XIV. of Professor Wood's Optics, where 

 that learned author <rives a mathematical investigation of the 

 number and arrangement of the images formed by two reflectors, 

 either inclined or parallel to each other. This theorem assigns 

 no position either to the eye or to the object, and does not even 

 include the principle of inversion, which is absolutely necessary 

 to the production of symmetrical forms. The theorem is true, 

 whatever be the position of the object or of the eye. In order to 

 put this matter to rest, Dr. Brewster wrote a letter to Professor 



