E. DoBSOK. — State of Applied Science in Canterhury . 141 



amount of sucli error, and tMs can readily be done. The permanent mark 

 on the central tower consists of a batten six inches wide, with a black stripe 

 one inch wide down its centre. The eye-piece of the transit instrument, 

 being furnished Avith five vertical wires, placed at equal distances apart, 

 the value of the space between any two wires, at a distance equal to that 

 of the mark on the tower, can be ascertained by reference to -the width 

 of the batten, which thus gives a scale by which the error in the position 

 of a light, placed in the tunnel under the tower, can be rated with great 

 exactness. 



Although it is not probable that any important extension of our railway 

 system can be undertaken at present, it is satisfactory to know that the 

 surveys of the Southern Eailway have been carried down to the Waitaki, 

 and connected with those made by the Eailway Engineer of the Otago 

 Province, and that the necessary reserves have been made so far as the lines 

 run through land belonging to the Grovernment. 



EiTEES. — During the last few years great changes have taken place in 

 the channels of some of our large rivers, both on the East and West Coasts. 

 The Eangitata has for some years past been scouring out for itself a new 

 channel down what is known as the Deep Creek, the original main river-bed 

 being now almost deserted by the water. It is worth putting on record 

 that this great change, which seriously affects a large extent of pastoral 

 country, had its origin in the cutting of a ditch to form a sheep boundary, and 

 the run of water thus established has gradually attained such dimensions as 

 to cause the^diversion of the greater part of the river from its original bed. 

 The Waimakariri, which used to deliver the great bulk of its waters through 

 the channel on the south side of the Kaiapoi Island, has shifted its course 

 into the north channel, (the quantity of water in the latter stream being 

 shown, by gauging, to be three times that in the former one), overflowing 

 its banks in many places, and seriously injuring the navigation of the river 

 by the amount of shingle brought down by the freshes. At the same time 

 the river has threatened to break through its banks about nineteen miles 

 from Christchurch, and to flow down to that town along channels which, 

 although long since dry, at some distant time have carried no inconsiderable 

 quantity of water. 



It is impossible to over-estimate the value of a continued series of obser- 

 vations made fi'om year to year to ascertain the nature and extent of the 

 changes going on in the courses of our rivers, and I would earnestly request 

 each of the members of the Institute to assist, so far as lies in his power, by 

 making careful measurements, from permanently fixed points, of all altera- 

 tions taking place in his own immediate neighbourhood. 



Aeteeial Deaina&e. — Passing from natural to artificial watercourses, 



