II. LENGTH. 59 



tide-measurer, moved to and fro by the rising and falling water, and by the 

 rotation of the glass disc, and may be read off at any desired intervals of 

 time. 



The calculation otherwise necessary of the mean water-level (the true level 

 of the sea) from the indications of the registering apparatus is saved by the 

 above-mentioned mechanical arrangement, and effected automatically with 

 very great accuracy by the tide-measurer. 



281. Self-recording Tide-gauge, improved. 



H. C. Ahrbecker. 



In this model the whole of the paper can always be seen, and requires 

 renewal only once a month. The clock goes for 32 days. 



282. " Mareegraphe," or tide-gauge. Van Rysselberghe. 



G. MISCELLANEOUS LENGTH-MEASURING INSTRUMENTS. 



238. Measuring Wheel for determining distance by regis- 

 tering the number of revolutions ; the upper index pointing out 

 every single and the lower every 100 revolutions. 



Elliott Brothers. 



238a. Odometer or Way Measurer in gilt metal case 

 elaborately chased, an early example probably made in the second 

 half of the 16th century. Alexander Nesbitt. 



In Beckmann's History of Inventions is a description of two instruments 

 resembling this, which belonged to the Emperor Rudolph II. (1576-1612). 



240. Improved Measuring Wheel or Mile Meter. 



Elliott Brothers. 



270. Holt's Diagrammeter. This instrument is specially 

 made for measuring the ordinates of indicator-diagrams 5" long, 

 and is used much after the manner of a parallel rule, the register- 

 ing nut on the screw being first placed at zero ; when it is required 

 to register a measurement the key for break is depressed, and when 

 all the measurements have been taken the distance the nut has 

 travelled gives the mean ordinate. Henry P. Holt, C.E. 



274. Spherometer (by Salleron), to read to "001 mm. 



The Council of the Yorkshire College of Science, Leeds. 



276. The Wealemefna. A pendant for the watch-chain. 



The Morris Patents Engineering Works, Birmingham. 



To measure, it is merely necessary to advance the Wealemefna over the 

 object, when the large hand will register the inches and fractions of an inch, 

 and the small one the feet. The instrument registers to 25 feet, 



277. Measuring Instrument, for the use of architects, 

 surveyors, builders, contractors, timber merchants, &c. &c., and 

 for general measuring purposes, in place of the rule or tape. 



The Morris Patents Engineering Works, Birmingham. 



