212 THE RANGE OF NATURE'S OPERATIONS. 



knowledge of the starry universe comes to an end. It is perhaps pos- 

 sible that the great nebula in Andromeda and a few other nongaseous 

 nebulai are stellar systems distinct from that of which the Milky Way 

 is the outlying portion, and which is commonly spoken of as the stellar 

 universe. If so, such of these other ' ^ universes " as can be visible to us 

 probably lie within a sphere which extends into the space beyond our 

 stellar system, perhaps some hundred times farther than the boundary 

 of the Milky Way, and may accordingly need, to represent the dis- 

 tances of some of them, numbers inserted in the next column of our 

 table (fig. 1). Accordingly, the column of metro-twentyones is in the 

 table indicated as one of those included within the range of what man 

 possibly already knows something about. 



From this preliminary survey it appears that man is only acquainted 

 with a strictly limited portion of the scale upon Avhich the r(>al opera- 

 tions of nature are being carried on. All her operations upon an ultra- 

 stellar scale, all her activities at infra-molecular degrees of proximity, 

 are kept from our view by that heavv veil of Isis which man's limited 

 senses and his restricted intellectual powers can not lift. It raises us 

 in the scale of thinking beings to see clearly where our knowledge 

 must end, and to have ascertained detinitely which part of the bound- 

 less range of nature's actual operations is that which human powers 

 are able to gauge and which human minds can adequately grasp. The 

 survey may be rendered definite with the help of the ta])le com})ris(Mi 

 in fig. 1, in which numerical digits are to take the place of some of the 

 ciphers. According to the place where we insert these numbers we can 

 make them express by how many meters, or by what fraction of a 

 meter, we are to measure any of the magnitudes with which man has 

 become acquainted throughout the whole range of his study of nature. 



In this table metros mean decimal nuiltiples of the meter; metrets 

 mean its decimal submultiples, and kllem (to be pronounced with the 

 i long,^ as in mile) is used as convenient English for the French ^'kilo- 

 meter." The first few places in the table, and the last four or five, 

 lie beyond the range of our present knowledge. Nevertheless, they 

 are included, in order that the table may not be unduly shortened by 

 temporary ignorance on our part, but may provide a large margin for 

 possible future discoveries. 



The significance of the survey is best appreciated l)y examining sepa- 

 rately the four groups into which the table is divided, audit is conven- 

 ient to begin with Group C, as it includes the measures most familiar 

 to us. 



GROUP C (laboratory MEASURES). 



Group C extends from kllems (kilometers) on the left, down to tenths 

 of^a micron on the right. The central subsection v includes the meas- 

 ures most in use in our laboratories, from meters down to tenths 



^In ;tiA.zds, "a thouaand," and in all Greek words derived from x^^t^ccc, the t is long. 



