878 • REPOKT— 1900. 



diaoram tlius obtained gives a direct measure of the speed and acceleration of tlie 

 carriage. 



The author showed that pendulum ohservations, combined with a record of 

 speed and power supplied, offer a simple and eil'ective means of determining tha 

 resistance to, and efficiency of, electric or other kinds of motor vehicles. 



7. On a Combination integrating Wattmeter and Maximum Demand 

 Indicator. By T. Barker. 



The paper fully sets forth the advantages of the maximum demand system of 

 charn-ing for the supply of electricity, and describes a new meter — the invention 

 of Messrs. Barker and Ewing — to be used for this purpose. The paper was illus- 

 trated by diagrams, and examples of the meter were exhibited. 



In charging for the supply of electricity it has become usual to make a dis- 

 tinction in the prices charged to those consumers who use a few lights for many 

 hours per day and those who use many lights for an hour or less ; for, although at 

 the end of the year the number of unirs consumed may be the same in both cases, 

 the cost to the company or corporation in macliiuery, mains, and every other charge 

 will be in the ratio of the number of lamps lighted at one time. The consumer 

 who uses a few lamps for many hours should be charged at a less rate per unit in 

 view of the smaller capital expenditure wliich his supply involves. 



The late Dr. Hopkinson advocated a system which takes account of this con- 

 sideration in arriving at the fair price to be charged for current. In the system in 

 question, now known as the ' Maximum Demand System,' the total quantity of 

 electricity consumed in six months is measured in the usual way, and the greatest 

 rate at which the consumer has been taking current is also recorded. If the con- 

 sumer in the six months' period takes a smaller total than would correspond to 

 one hour a day at the greatest rate of demand, he is charg'^d the full price per 

 unit, but if the total consumption exceeds this he is charged a reduced rate for 

 each unit in excess. 



The system has been used with marked success in some seventy-two towns. 

 It has improved the load factor, and has enabled a large number of additional 

 units to be sold without increase of station plant or mains. Until the introduc- 

 tion of Barker and Ewings Demand Indicator it was necefsary to use two meters 

 — one to record the total number of units taken by the consumer and the other to 

 sliow his maximum rate of demand. 



The Barker and Ewing Indicator forms an integral part of the ordinary meter, 

 and absorbs no energy ; it further records watts and not amperes. With an alter- 

 nating supply it shows actual watts and not apparent watts, an important diti'erence 

 in the case of motors and arc-lamps. It is not affected by any ordinary short circuit, 

 its time lag being sufficient to prevent it coming into action. The Indicator may 

 be used to show the actual rate of demand at any instant in place of recording the 

 maximum rate of demand. In this form it is specially useful in switchboard 

 instruments, showing the attendant the rate at which electric energy is passing 

 through a feeder or is supplied from a dynamo at any instant. The meter also 

 serves at the same time to integrate the total amount which has passed through 

 that particular feeder or machine. 



8. The Design and Location of Electric Generating Stations. 

 ISy Alfred H. Gibbings, M.Inst.E.E. 



The term ' central station ' is gradually being supplanted by more comprehen- 

 sive designations. 



All design and arrangement in regard to electric works must be with a view- 

 to securing the highest average efficiency together with reliability in operation. 

 Electric works at present do not fulfil these conditions, but that may excusably 

 be accounted for because it was impossible to foresee modern developments. 

 Electricity, at first used for lighting only, has now come to be used in the form 



