258 The Microscope. 



application to a very narrow field of research. "Where the telescope 

 answers a single question the microscope answers a thousand. 

 Spectroscopy has become a recognized science, not so much because 

 of its revelations in regard to the nature of light, as on account of 

 the application of the spectroscope as an instrument to the study of 

 the physical properties of matter and of motion not only on the earth 

 but in worlds other than our own. 



In discussing the question whether microscopy can be regarded 

 as a science, we must always bear in the mind the fact that a science is 

 only a convenient name for a group of similar laws of nature, and 

 that the term is properly applicable not only to the development of 

 the laws but to 'their application to the useful economies of life. 

 Thus we have the science of engineering in which mathematical 

 analysis is as much an essential part as skill in mechanical construc- 

 tion. But this analysis would serve no useful purpose if it did not 

 rest ultimately on facts of observation. 



The limitations which necessarily belong to a definition of physi- 

 cal science are clearly expressed by Tate in his most admirable 

 treatise on Heat. He says : " Nothing can be learned as to the 

 physical world save by observation and experiment, or by mathemati- 

 cal deductions from data so obtained.''^ Now the microscope as an 

 instrument of research stands unrivaled not only in respect to the 

 precision of the observations made with its aid but also in the 

 university of its application in furnishing what Tate calls " the data 

 so obtained." Each succeeding year witnesses an extension of the 

 range of its applications. Within a few years, while retaining its 

 claim as an essential factor in scientific research, it has also become 

 a veiy material aid in many mechanical industries. It is a common 

 impression that the microscope is too delicate an instiTiment to be 

 used in the ordinary operations of mechanical construction, and that 

 the apparent necessity of using transmitted light for the purpose of 

 illumination is an absolute barrier to any extended employment of 

 the instrument. The latter difficulty is entirely obviated by the use 

 of the opaque illuminator, invented by Tolles, by which a bright 

 metal surface can lie examined with the utmost ease, while actual 

 experience has shown that it is by no means necessary that the 

 instniment shall be mounted upon massive piers insulated from 

 surrounding objects. I cannot more forcibly combat this impression 

 than by referring to two cases within my own experience. The 

 Proceedings of the Society of Mechanical Engineers for 1887 contains 

 a description of a method of cutting a screw in which each thread is 



