M 



NA TURE 



[April 14, 1898 



Here the work is based on the original ordnance survey 

 maps, and the topographical details filled in from photo- 

 graphy. These maps represent one of the most suc- 

 cessful applications of photographic surveying. Again, 

 in preliminary experimental surveys for irrigation 

 purposes, or for deciding on the best route for a proposed 

 railway, the camera, properly controlled, possesses many 

 advantages over ordinary surveying instruments. In such 

 cases it is often excessively difficult to determine 

 beforehand how much plotting will be necessary to 

 secure the object in view. The district may have to be 

 re-visited over and over again to supply the requisite 

 details, all of which may prove useless in the end. But 

 with the photographic pictures secured by a camera, the 

 plan may be plotted so far only as required, and if 

 additional information be needed, the photographs can be 

 made to give all the detail wanted without going again to 

 the field. Irrigation surveys for agricultural purposes 

 have been effected in the North-West Provinces with 

 complete success by the photographic method, and are 

 Hkely to be still further extended. Prof. Mills tried to 

 apply the method to the determination of the content of 

 a ship in dock by constructing a model of the vessel in 

 clay, the necessary dimensions for which were to be 

 taken from measured photographs. When the amount 

 of clay in the model, and the scale of the photograph 

 from which the necessary measurements have been taken 

 are both known, the capacity of the ship is at once 

 determined. In this particular instance, it is true, the 

 method failed, owing to the impossibility of selecting 

 suitable stations for the photographs amid the crowded 

 machinery of a busy ship-building yard. But the attempt 

 shows the wide applicability of the method and the ex- 

 tent of the field open to the intelligent use of photo- 

 graphic appliances. 



But its greatest triumphs are, of course, to be seen when 

 the method is continuously applied over a large area. One 

 of the most successful operators is Mr. E. Deville, the 

 Surveyor General of Dominion Lands, who has carried 

 his investigations over the difficult passes of the Rocky 

 Mountains, and surveyed the country up to the United 

 States boundary of the Alaska territo y. No less than 

 14,000 square miles of this inhospitible country were 

 surveyed in the years 1893-94. The proper administra- 

 tion of the country, he tells us, required a tolerably 

 accurate map, and means had to be found to execute it 

 rapidly, and at a moderate cost. The ordinary methods 

 of topographical surveying were too slow and expensive 

 for the purpose ; rapid surveys, based on triangulations, 

 and sketches were tried and proved ineffectual ; then 

 photography was resorted to, with the result just 

 mentioned. The same authority, as was natural to one 

 in his official position, has made a very careful comparison 

 of the relative expense of a survey made with the plane 

 table and one with the camera : all such comparisons are 

 liable to be modified by the climatic conditions of the 

 country, and the amount of detailed plotting required. 

 In the climate of the Rocky Mountains, Mr. Deville 

 estimates that on one half of the number of days in a 

 season, no work can be done with a camera, owing to 

 smoke, fog, rain and snow storms. But quite as great a 

 loss of time is experienced with the plane table, added to 

 which the apparatus is more weighty, requiring more 

 porterage, and therefore additional expense in removal. 

 But neglecting these and some other slight advantages 

 which are on the side of photography, he finds that the 

 plane table survey is three times (rigorously as 164 : 56) 

 more expensive than that accomplished by the camera. 

 This is a real practical advantage which is immediately 

 appreciated, and on several grounds, not taken into 

 Mr. Deville's estimate, such as the possibility of reduc- 

 ing the number of highly-trained assistants, it would seem 

 that the difference of expenditure has not been over- 

 estimated. There is no sacrifice of accuracy to secure 



NO. 1485. VOL. 57] 



this economy ; the great improvement consists in the sub- 

 stitution of the methodsof photography— methods, which 

 proving highly popular, must tend to displace more and 

 more the use of the plane table. 



BALNIBARBIAN GLUMTRAP RHYME. 



{Repeated by the children in the nurseries of Balnibarbi.) * 



■p\ISTANT scintillating star, 

 -*-^ Shall I tell you what you are ? 

 Nay, for I can merely know 

 What you were some years ago. 



For, the rays that reach me here 

 May have left your photosphere 

 Ere the fight of Waterloo— 

 Ere the pterodactyl flew ! 



Many stars have passed away 

 Since your jether-shaking ray 

 On its lengthy journey sped — 

 So that you, perhaps, are dead ! 



Smashed in some tremendous war 

 With another mighty star — 

 You and all your planets just 

 Scattered into cosmic dust ! 



Strange, if you have vanished quite, 

 That we still behold your light, 

 Playing for so long a time 

 Some celestial pantomime ! 



But, supposing all is well. 

 What you're made of, can I tell ? 

 Yes, 'twill be an easy task 

 If my spectroscope I ask. 



There — your spectrum now is spread 

 Down from ultra-blue to red. 

 Crossed by dark metallic lines, 

 Of your cooler layer the signs. 



Hence among the starry spheres 

 You've arrived at middle years — 

 You are fairly old and ripe, 

 Of our solid solar type. 



Ah, your sodium line is seen 

 Strongly shifted towards the green. 

 Hence you are approaching me 

 With a huge velocity ! 



But, if some celestial woe 



Overtook you long ago. 



And to swift destruction hurled 



Life on every living world, ■'■^ 



Did there in the fiery tide 

 Perish much of pomp and pride — • 

 Many emperors and kings. 

 Going to do awful things ? 



Mighty schemes of mighty czars — 

 Mighty armies, glorious wars ! 

 From the Nebula they may 

 Rise to curse a world some day ! 



G. M. MiNCHIN. 



1 Balnibarbi is one of the countries visited by Gulliver ; the " Glumtrap' 

 is the Balnibarbian equivalent of the English nursery ; and the babies of 

 Balnibarbi are brought up on strictly scientific principles — as is evidenced 

 by their knowledge in these verses. 



.J 



