884 EEPORT— 1887. 



This is the case when the hammer cylinder is cold ; when liot the average 

 driving pressure falls to 20 lbs. per square inch and the blow to 3-19 cwt., falling 

 through a foot, or 358 foot-pounds. The gas used is 1 cubic foot for 94 of the 

 latter blows. 



Birmingham gas with which these experiments were made costs 2^-. Gd. per 

 1 ,000 cubic feet or 33 cubic feet for one penny, and 33 x 94 = 3,102 blows are thus 

 obtained at the cost of one penny. This is an exceedingly economical and satis- 

 factory result. 



The paper concludes with a statement of the several purposes to which tliis 

 hammer can with advantage be applied. 



11. On the British Association Standard Screiv Gauge. 

 Bij W. H. Preece, F.B.S. 



Owing to the large number of telegraph instruments made by different manu- 

 facturers the number of screws of different forms and sizes in use was very great, 

 and this was found to be a great disadvantage and a great source of expense. 

 When the Post Office commenced to manufacture its own apparatus it was 

 decided to make all parts to template, so as to be interchangeable ; and it was also 

 decided to adopt some standard for screws. The standard recommended by the 

 Committee appointed by the British Association is now being introduced in all 

 instruments and apparatus manufactured by and for the Post Office Department, a 

 circular to that effect havhiy- been issued to all lirins manufacturing for the 

 G.P.O. 



A set of standard taps and plates was exhibited. 



12. A Fire-damp Indicator. By J. WiLSOX Swan. 



13. On an improved Bailway Beadinrj Lamp. Bij W. H. Peeece, F.B.S .^ 



