550 



NATURE 



[February 22, 191 2 



from a constructional point of view, totally wronjj, and 

 this is proved by the fact that ev«-n these slides are ground 

 to fit in the first course of manufacture, and that the 

 spring's are cut and adjustment screws provided afterwards 

 in order to take up the looseness and shake which has 

 already developed before the instrument has left the work- 

 shop ; this will be borne out by any person with practical 

 experience. 



The perfectly constructed and accurately machined slide 

 bearings adopted on the Continental microscopes only re- 

 qiiii'' sliiiht liiiiulin^; in, and consequently last for a con- 

 V 1. n^tli of time, and if returned to the 



11, iiu^tiii. Ill, the substage, condenser, and 



i)bji itivLS arc recentred by any house which has a reputa- 

 tion worth maintaining. 



Objectives provided with correction collars are now 

 almost a thing of the past, as cover-glasses of a near 

 definite thickness are no longer diflficult to obtain, and 

 what slight correction may be necessary can be effected 

 by an easy working draw-tube of the sliding type, which 

 can be adjusted to a nicety by adopting a twisting motion 

 when moving the tube either up or down. 



1-ondon, February 19. F. R. Brand. 



On Martian Detail. 



The present seems to me a fitting time to publish the 

 results of nearly three years' investigation of the above 

 subject. In the pursuit of this investigation I have visited 

 most of the principal observatories in the world and tested 

 their seeing conditions, and I conclude categorically that 

 thf climate at Flagstaff is immeasurably superior to that 

 of any other observatory with which I am acquainted. At 

 Flagstaff — by the means which experience has proved to 

 be the best — Mars is so well seen that it is oifTicult to 

 believe it the same planet, the grotesque caricatures of 

 which are apt elsewhere to mislead the observer. 



No one elsewhere seems to have realised the fundamental 

 postulates of visual work, the first of which is that small 

 apertures always define better than big, and that if 

 we set a minimum of 12 to 15 in. any increase on this 

 causes a loss of defining power. 



That this is not generally known is witnessed by the 

 scepticism of the leading optician of the firm of Alvan 

 Clark, which" however, vanished when he performed the 

 experiment here a few years ago. It is therefore a priori 

 impossible to corroborate with vast apertures of 30 to 

 60 in. the results to which the smaller ones have led us. 



In the face of the postulate above stated, it is impossible 

 to believe the work of great apertures. It would be 

 difficult to see why' so much confidence has been placed in 

 them were it not for the fact that those who uphold them 

 have up to now never tested the truth of our postulate. 



I have even met observers who averred that dark glasses 

 were unnecessary when the planet dazzled the eye. 



Those who could overlook this necessity may easily be 

 blind to all other refinements of instrument and observer. 

 That reduction of aperture means improvement of defini- 

 tion may be tested by anyone at any time with any 

 instrument, and none but the wilfully blind can fail to be 

 convinced. 



When the above precautions are duly taken the canals 

 are seen with a geometric reality, fineness, and clearness 

 that is amazing. When so seen, the very strangeness of 

 the sight at once suggests and demands the explanation 

 that they are not natural, but artificial, features of the 

 planet — the work of reasoning beings, whose purpose we 

 can divine. Those who discredit the immortal discoveries 

 of Schiaparelli and Lowell have never learned how to 

 observe them, being wilfully or accidentally without know- 

 ledge of the proper method of seeking them. 



In pursuit of this investigation I have used all apertures 

 fron^ 2 in. to 60 in. 



No doubt remains in my mind as to the objective reality 

 of what I have seen, and therefore with entire confidence 

 I endorse the discoveries of Schiaparelli and the further 

 advances made by Lowell in the same investigation. The 

 latter has also set forth what I deem the onlv rational 



explanation conceivable to account for this most ar 

 concatenation of observed phenomena. 



Further, I would point out to your readers that Lo« 

 explanation is the only complete and consistent one 

 put forward, and that it can only be replaced by an eqi 

 complete one, and is not to be combated by the isol 

 and conflicting statements of biassed and partial judgr 

 which up to now have been brought against it. 



James H. Worthi\cton._ 



Lowell Observatory, Flagstaff, Arizona, January 22. 



A Simple Automatic Syphon. 



The accompanying diagram illustrates a form of ajj 

 matit syphon which has been found useful in cases 

 it is desirable to draw off wdt#-r^from the bottom of a 

 at the same rate as it is supplied at the top. This 

 particularly important when the 

 water has to be kept saturated 

 with air. 



The diagram represents an 

 ordinary syphon of glass tube, 

 the opening into the tank being 

 ground to the form of a cone. 

 •Above this end is a float, con- 

 sisting of a glass bulb and open 

 glass stem filled with air. The 

 lower end of the stem is ground 

 to fit over the conical end of the 

 syphon. Water thus escap<-~ 

 from the bottom of the tank 

 through the annular span 

 between the ground portion>, 

 and the float automatically 

 adjusts itself so that the rate of 

 flow of water through the syphon 

 is exactly the same as the rate 

 at which water enters the tank. 

 Should the supply of water 

 cease, the float sinks and closes 

 the syphon. 



The syphon is conveniently 

 fixed by passing one, limb through 

 a cork cemented on to the out- 

 side of the tank. The weight of the tube maintains the 

 float in a vertical position, while the ground end of th« 

 syphon tube keeps it stationary in the tank. 



Charterhouse, Godalming. J. C. 



Thomson. 



Glazed Frost. 



During the two winters that I lived in Massachusetts, 

 glazed frosts, or " ice storms " as they were called therei 

 were of comparatively frequent occurrence. I can recaD 

 three or four at least. 



The ice storm always came after a period of very coM 

 weather, when the temperature had been down to zero or 

 below for some days. Suddenly the frost would break, and 

 the thermometer rose to 32° or 33° F., the sky became 

 I overcast, and a heavy drizzle began to fall, driving before 

 a slight wind, usually from the west. As the rain fdl 

 it froze in a clear layer upon everything exposed to H$ 

 course. Trees, pavements, tram-lines, and overhead wire* 

 were covered in an hour or two to as much as i inch in 

 thickness. The trams and trains had to stop runnio 

 owing to the state of the rails, whilst even the thi«; 

 trolley wires were unable to support the weight of tl 

 incrustation, and branches as much as 6 inches thick wel 

 broken from the trees everywhere. ^ 



The storms always came on in the morning. Abowt 

 noon the rain stopped, the clouds cleared away, and tip 

 sun came out. The diamond-coated branches, 

 showers of silvery drops falling from them, against 

 dark blue .American sky made a scene the beauty of wh 

 can scarcely be imagined. W. Ermen^ 



10 Marsden Street, Manchester, February 16. 



NO. 2208, VOL. 88] 



