184 report — 1865. 



as much. In like manner, india-rubber absorbed 0177 grain at a lower tempera- 

 ture, and 0-45 at a higher, or two and a half times as much. Wray's compound 

 0-072 at a lower temperature, and 058 at the higher, or seven times as much. 



In the earlier experiments the insulating power of the various cores was tested 

 with voltaic electricity. In the following series, however, recourse was had to 

 frictional electricity, which from its high intensity passed with greater or" less 

 facility through the insulating coverings of the wire. In the former, the measure- 

 ment and regulation of the charge, and the rate of loss were made with a double 

 pith-ball electrometer; in the latter, or fifth series, a Peltier's electrometer was 

 employed. 



The charge was given from an electrophorus, and was ordinarily of such inten- 

 sity as to deflect the needle through an arc of 70°. The fall of the needle was 

 watched at intervals till it had sunk to 20°. 



On a careful inspection of the above summary, it will be seen that a great differ- 

 ence exists in the retentive powers of the different cores or insulators under severe 

 pressure, which in these anomalies almost defy attempts at comparison. The expe- 

 riments are, however, satisfactory, in so far as they show approximately the relative 

 porosity of various materials ; but they do not point out how Ave are to obtain an 

 insulator impermeable to water, and at the same time a good non-conductor. This 

 desideratum has yet to be attained. 



Suggestions for Improvements in Bloclcs for Loivering Ships' Boats, and for 

 Improvements in Boats. Bg Geokge Fawctjs. 



Blocks were exhibited, in which the vertical and lateral pressures of the weight 

 suspended were directed (by a combination of levers) to disengage the hooking 

 parts which moved on eccentric bearings. 



In the boats accumulated strength was given (to all the parts liable to alter) 

 with the utmost compactness ; and with all the detailed requirements these boats 

 of the same size packed together indiscriminately. 



District Privecte Telegraphs. Bg Nath. J. Holmes. 



The introduction and use of private telegraphs in this country is of comparatively 

 recent date. The apparatus in use upon the railways in signalling trains, and by 

 the telegraph companies for the transmission of public messages, is unsuitable for 

 the requirements of the private telegraph. The employment of conventional signs, 

 and what is technically known as the "dot and dash" system, renders the signals 

 unintelligible except in the hands of properly trained clerks. In 1840 Prof. Wheat- 

 stone patented his first alphabetical telegraph. 



This instrument has since been greatly improved, and another patent was taken 

 out in 1858, from which year the general introduction of private telegraphs may 

 be dated. The first private lines erected in London under the new system were 

 those of Messrs. Spottiswoode, Messrs. Waterlow and Son, and the London Dock 

 Company- 



In the year 18G0 Prof. Wheatstone and Mr. Nath. J. Holmes established the 

 present Universal Private Telegraph Company for the purpose of providing private 

 wires in various parts of the kingdom upon a system of annual rentals. This Com- 

 pany, afterwards incorporated in 1861, has already extended its system to every 

 important town and district in the kingdom, and during the last four years has 

 erected upwards of 2000 miles of private wire, employing 863 sets of instruments. 



On the Applicability of India-rubber as an Insulator for Telegraphic 

 Conductors. By W. Hooper. 



The author noticed the difficulties encountered in applying caoutchouc for insu- 

 lating purposes, describing the decay of caoutchouc, especially when exposed to air 

 and light, arising from oxidation, and resulting in a condition of fluidity. In apply- 

 ing caoutchouc as an insulator, it has been generally washed, dried, and masticated, 

 being manufactured by the process into solid blocks, which are then cut up into 



