472 SPECIAL METHODS OF DISCOVERT. 



of existences in space ; of the arrangements and quantities 

 of masses of matter ; of the direction, distribution, and 

 amount of cohesive and adhesive forces ; the direction, 

 intensity, distribution, mode of propagation, and velocity 

 of light and radiant heat ; of phosphorescence, fluorescence, 

 conduction, and convection of heat ; the distribution, direc- 

 tion of action, intensity and amount of electricity ; the 

 direction and velocity of electric conduction ; the distri- 

 bution, strength, and velocity of transmission of mag- 

 netism ; the distribution, amount, and velocity of chemical 

 affinity ; the velocity of nervous and mental action, &c. &c. 

 The invention of a new instrument is in some instances 

 almost equivalent to the acquisition of a new sense : for 

 example, by means of the polariscope we are enabled to 

 perceive a new class of phenomena which our unaided 

 senses do not enable us to perceive in any degree ; and a 

 nearly similar remark may be made with regard to the 

 spectroscope and the electric telephone. In other cases, the 

 invention of a new instrument greatly extends the range 

 of application of our powers, and thus enables us to dis- 

 cover new truths. By the invention of the simple mecha- 

 nical powers the lever, wedge, screw, axle, pulley, and 

 their various combinations we have been enabled to pro- 

 duce a variety of new mechanical effects and evolve many 

 new truths of mechanical philosophy. By the inven- 

 tion of the hydrostatic press, we have been enabled to 

 apply immense pressure to liquids, and to discover new 

 truths respecting them ; by the invention of the oxy- 

 hydrogen blowpipe and electric lamp, we have been em- 

 powered to obtain far more intense heat and light, and 

 by means of those forces to make many new discoveries ; 

 and so on through almost the entire list of instruments 

 we employ. The assistance of an instrument is equivalent 

 to an enormous extension of our senses, in the example 



