THE PLANET MARS 123 



again — and seeing them better with growing experience, he 

 added to their number and complexity the fact that many ot 

 them consisted of doublets the two component lines of which 

 were rigidly parallel. 



Those who could not see the "canali" at all very naturally 

 refused to give credence to them and began to suspect that they 

 were the illusions of their discoverer. 



As first seen by Schiaparelli, they were not by any means 

 very regular but as his powers of discrimination increased with 

 practice, he perceived more and more clearly their linear and 

 geometric configuration. 



To see these markings at all implies a very great advance in 

 the observer's art, as is proved by the fact that even to this day, 

 though their existence is no longer questionable or questioned, 

 there are few observers who have seen them as well as did their 

 discoverer more than thirty years ago. 



The object of this article being to present concisely an 

 account of our present knowledge of the planet, we shall do 

 well to proceed at once to study the methods used by Lowell— 

 Schiaparelli's greatest successor — and the results which he has 

 obtained. Lowell has added more to our knowledge of the 

 planet than the sum total of all that we previously possessed. 



At his observatory the mathematical appearance of the 

 11 canali " has been confirmed and the discovery of an equally 

 amazing and correlated system of spots — which he calls oases- 

 has been added. 



Another advance was made by the detection in the green 

 areas of the uninterrupted continuance of the network of the 

 "canali," thus showing them to be limited in extent only by the 

 surface of the planet on which they occur. 



In order to appreciate the weight ot conviction which these 

 discoveries carry, it is necessary to enter somewhat minutely 

 into the means and methods by which they have been achieved. 

 I shall therefore describe them as best I may. 



It is often thought, by those unfamiliar with planetary 

 observations, that the larger the telescope the more detail it 

 should reveal ; the first step therefore will be to remove this 

 cardinal misconception by a careful consideration of the optical 

 principles involved in the scrutiny of detail upon a planetary disc. 



The problem may be succinctly stated as follows : Given a 



