Jan. 21, 1875] 



NA TURE 



233 



= I + 



V 



A very simple formula, in which the original number of 

 waves disappears, showing that the interval between the 

 two notes is irrespective of the original pitch of the whistle, 

 and depends only on the velocity with which the listener 

 approaches the source of the sound. 



We have now to take the case where the listener, having 

 passed the whistle, is receding from the source of sound. 

 The note will then appear flatter than the real one, and 

 its vibration number will be found by the same rule as 

 before, merely giving v a minus sign. 



= '<■ - ;■) 



And the intt-rval, i.e., the ratio [of the vibrations of the 

 higher to that of the lower, denoted by 8j will be 

 n V 



«(' - f) 



V 



These two intervals added together will express the drop 

 of pitch of the whistle at the time of passing. 



IJut to add intervals together we must multiply their 

 ratios ; hence if 8., represent the drop, 



«•. = P^ 

 V - V 



from which the drop of the whistle corresponding to any 



speed may be found. 



To simplify the reasoning, we have supposed the whistle 

 to be stationary and the listener to move with a velocity 

 = V. If both move, as is the usual case in railway trains 

 meeting, v must be made = the sum of the speed of the 

 two. 



Taking K = 1 1 20 feet per second for ordinary condi- 

 tions, the following table shows the value of the drop for 

 different speeds : — 



I have made observations whenever I have had the 

 opportimity, and find the results corroborate the deduc- 

 tions of theory. The most common interval observed in 

 ordinary travelling is about a third, major or minor, cor- 

 responding to a speed of between thirty-five and forty 

 miles per hour for each train. \V. Pole 



GLASGOW SCIENCE LECTURES 



UNDER the title of the Glasgow Science Lectures 

 Association, an organisation has lately been formed 

 in Glasgow, whose object is to provide annual courses of 



lectures on various branches of science by men of 

 eminence in each department, so as to place in clear and 

 comprehensive outlines the most important results of 

 scientific inquiry before the public of Glasgow, and at 

 such a rate as will secure to those who cannot otherwise 

 obtain it the best information on the state of science, as 

 established by the most recent investigations of its most 

 distinguished workers. The scheme originated amongst a 

 number of working men who were desirous of following the 

 example of the science lecture movement which has been 

 so successfully worked out in Manchester during the last 

 six or seven years, but with this difference, namely, that 

 the lectures should be self-supporting. To accomplish 

 that end, and be in a position to pay the lecturers liber- 

 ally for their services, they at once saw that the minimum 

 rate of admission could not well be fixed at less than 

 threepence, and they confidently believed that many of 

 their fellows would be most willing to pay that amount 

 for the privilege which it was proposed to place within 

 their reach. They soon enlisted the sympathies and 

 active co-operation of persons in a higher social sphere, 

 and in due time the Association took active shape. A 

 large executive committee was constituted, and Dr. 

 Allen Thomson, F.R..S., one of the most distinguished 

 members of the professorial staff of the University of 

 Glasgow, cheerfully accepted the honorary presidentship 

 of the Association, while a number of oiher prominent 

 citizens were enrolled in the list of vice-presidents. 



Owing to the fact that Prof. Roscoe had been the 

 moving spirit of the Manchester Science Lectures for the 

 People, he was very early communicated with, in the 

 confident hope that valuable advice based upon his 

 practical experience would readily be placed at the service 

 of the originators of the Glasgow lecture scheme. They 

 were not disappointed in their expectations, and, indeed, 

 had they been lacking in enthusiasm and determination 

 to make the scheme a success, they would have been 

 stimulated to action by the various communications which 

 they received from that gentleman. 



It was very late in the past year before the Glasgow Sci- 

 ence Lectures Association was sufficiently well organised 

 to make any public announcement of its existence ; but the 

 active promoters of the movement were most anxious not 

 to allow the whole winter to pass without having some 

 lectures delivered under the auspices of the Association, 

 no matter how short the course might be. Prof. Roscoe 

 most kindly and cheerfully consented to take part in the 

 first or introductory course ; and considering that gentle- 

 man's peculiar relationship to the Manchester Science 

 Lectures, the committee came to the conclusion that no 

 person could more appropriately assist at the public in- 

 auguration of the movement in Glasgow. Accordingly, 

 with his consent. Prof Roscoe was set down to deliver 

 the opening lecture of the introductory course, and other 

 three distinguished men of science were selected to 

 follow him, namely, Sir William Thomson, Dr. W. B. 

 Carpenter, and Prof. W. C. Williamson, of Owens College, 

 Manchester. 



The inaugural lecture was delivered on the evening of 

 Friday, the 8th of January, and it was in every sense a 

 most auspicious beginning. The Glasgow City Hall was 

 chosen as the place for the delivery of the lectures, as the 

 committee were desirous of bringing together the largest 

 audiences that could be convened in any place of public 

 meeting. It holds well-nigh three thousand persons, and 

 on the occasion in question it was crowded. The recep- 

 tion given to the eminent lecturer was most enthusiastic. 

 Dr. Thomson occupied the chair, and in introducing Prof. 

 Roscoe to the meeting and formally opening the first 

 course of lectures, he delivered an exceedingly valuable 

 address, in the course of which he justified the formation 

 of such associations as the one under whose auspices the 

 lectures were to be given. He said that he had no doubt 

 that in the selection of the lecturers the committee of the 



