278 



SCIENCE-GOSSIP. 



CONDUCTED BY JAMES QUICK. 



Electric Rail Welding.— In the "Electrical 

 World and Engineer " recently appeared a descrip- 

 tion of the electric rail welding plant of the Lorain 

 Steel Company, Ohio, as employed in making 7,500 

 rail joints in the Buffalo street railway system. The 

 trolley wire current is transformed by a rotary con- 

 verter carried on the car into single-phase current of 

 300 volts pressure, and then down to 5 or 7 volts by 

 another special transformer. The pressure being so 

 greatly reduced the current obtained is enormous, 

 as much as 25,000 amperes being produced. The 

 joint is made by means of fish-plates, welded on to 

 either side of the web under heavy pressure. Each 

 joint takes fifteen minutes to complete. 



New Reading Microscope. — Following upon 

 the description in last month's Physics column of the 

 vernier microscope, made by Messrs. John J. Griffin & 

 Sons, Limited, we here illustrate two additional instru- 

 ments made by this same firm for somewhat similar 

 purposes: i.e. the measurementof small distances. The 

 first of these is a reading microscope, the design being 

 an improvement upon that described in the course 

 of instruction in Practical Physics at the Royal 



The instrument is provided with an extra fitting as 

 shown enlarged in the top left corner of the illustra- 

 tion, so that the microscope may be used for either , 

 horizontal or vertical measurements. The instrument 

 has an English objective and a No. 1 eyepiece fitted 

 to the microscope tube, and is proving very useful in 

 numerous physical measurements, such as thermp- 

 meter calibration, indices of refraction, &c. The in- 

 strument is made entirely of brass, so that it may be 

 used in connection with magnetic measurements ; 

 otherwise, if iron was present in any of its parts, it 

 would interfere with the readings owing to magnetic 

 induction. 



A Point-cathetometer. — The second instru- 

 ment is what is known as a point-cathetometer, and 

 is also intended for the rapid measurements of vertical 

 distances, but greater ones than the above referred-to 

 instrument is adapted to measure. Into a firm iron 

 tripod base, which is provided with levelling screws, a 

 vertical brass tube about 1 m. long and of 2 to 

 3 cms. diameter is screwed. This tube is accu- 

 rately engraved through- 

 out its length into milli- 

 metres. Over the tube 

 slides a brass collar 

 which has a stiff rod fixed 

 to it and bent as shown 

 in the illustration. The 

 length of the collar is 5 

 cms., so that when it is 

 pushed down to the base 

 its top edge will read 5 

 cms. The length of the 

 rod is such that when the 

 collar is in this lowest 

 position the point of the 

 rod approximately 

 touches the table, lati- 

 tude being given by the 

 levelling screws upon the 

 base. Suppose now the 

 difference in height be- 

 tween two liquid columns 

 is required ; the collar is 

 pushed up until the point 

 of the rod is on a level 

 with the surface of one 

 of the columns, and the 

 reading is then taken. A 

 similar measurement is 

 made with the other 

 column, when the differ- 

 ence in height at once is 

 given. In numerous 

 other physical experi- 

 ments the point-cathetometer is useful. In fact it has 

 become quite a desideratum in a physical laboratory. 

 Messrs. Griffin also make a cheaper cathetometer in 

 which the graduated brass tube is replaced by a firm 

 boxwood scale. 



College of Science. Upon a rigid brass horse- 

 shoe base is fixed a substantial brass tube, at the 

 top of which is fitted a double rack and pinion 

 working the tube carrying the microscope, &c. 

 This tube has fixed to it and moving with it a 

 vertical scale, accurately graduated into millimetres. 

 By means of a vernier attached to the fixed pillar, 

 vertical distances of -j' n th mm. can be easily read off. 



Thawing Water-pipes with Electricity. — 

 From the "Canadian Electrical News" we learn 

 that frozen water service pipes are there thawed by 

 means of alternating currents of electricity passed 

 through the pipes themselves. A pressure of 20 to 

 50 volts is used, obtained from a portable transformer 

 connected with the street mains. A current of 200 

 to 400 amperes is passed through the frozen pipe 

 until the water flows freely, which usually takes place 

 in a few minutes. 



