184! R. S. Brough — Best Besistance of a [August, 



was glad to observe that considerable advance had been made. Notices o£ 

 nearly 1200 MSS. had been prepared in Sanskrit, and, if some of those 

 members who took an interest in the ancient classics of India, would turn 

 their attention to the subject, and superintend the translation and publica- 

 tion of those notices, the work, the first part of which he had the honor to 

 submit to the meeting, could be broght to an early completion. He was 

 glad also to announce that he had on hand an analysis of the very 

 valuable Sanskrit Buddhist MSS. which had been brought from Nepal by 

 their distinguished associate Mr. B. H. Hodgson, and four forms of the 

 work were already in type. 



The following papers were read : — 

 1. A theoretical deduction of the best Resistance of a Telegraph Receiving 

 Instrument. — By R. S. Beough. 



The information given in the text-books regarding the proper resis- 

 tance of an electro-magnetic receiving instrument to employ on any Tele- 

 graphic circuit is meagre and indefinite. The authors usually content 

 themselves with saying that on short circuits the instruments should be 

 wound with thick wire, while on long circuits they should be wound with 

 fine wire. 



Professor Fleeming Jenkin in his "Electricity and Magnetism", how- 

 ever, states that the resistance of the receiving instrument should not be more 

 than a moderate fraction of the resistance of the whole circuit. In a foot 

 note he adds that some authority (un-named) recommends that the resis- 

 tance of the receiving instrument should be j% of that of the whole circuit, 

 and remarks that this appears to be a very large value. 



Mr. Schwendler in his " Testing Instructions", published under the 

 authority of the Director General of Telegraphs in India, taking into con- 

 sideration the influence of want of perfect insulation of the line wire, 

 deduces that the resistance of the receiving instrument should be f of that 

 of the line wire. 



The fact of the matter is that on comparatively short lines, and at 

 low speeds of signalling (say 12 words per minute) the resistance of the 

 receiving instrument is not of much importance, as deficiency of sensibility 

 can be compensated by increased battery power, and the circuit will appear 

 to work equally satisfactorily whether the resistance of the receiving in- 

 strument be 500 or 2500 ohms. 



In such cases the general rule given in the Text Books is sufiicient for 

 practical purposes. 



When we come, however, to the case of high-speed signalling,* or 



* For high-speed Telegraphy, electro-magnetic receivers are being superseded by 

 ekctro-chemical receivers, which are free from mechanical and magnetical inertia. 



