344 



NATURE 



\_August 7, 1^79 



M. Cavaill^-CoU gives two examples of applications he 

 made of this formula : — 



1. A wood pipe sounding what is called 4-foot C, 264 

 [single] vibrations per second at the normal French 

 pitch, and having a depth of 8 centimetres, was found to 

 have a length of i^'is. Taking the velocity of sound at 

 10° to 15° C. to be 340 metres per second, the equation 

 would give — 



3|9_o-i6= i"-i28, 

 264 ' 



differing only 2 millimetres from that actually found. 



2. The large 32-foot pedal pipe of the organ of St. Denis 

 was at first cut to a length of 9™'s66, the internal depth 

 being o™"48. The number of single vibrations per second 

 was intended, according to the standard pitch, to be 33, 

 according to which the equation gave — 



^^-o-96 = 9"-36 



as the calculated length. This showed the pipe to be too 

 long, which proved to be the fact, the note being too 

 flat. An opening was then made to reduce the effective 

 length to that given, when the pipe was found to be in 

 perfect tune. 



In applying the formula to cyltndricai pipes, M. Cavailld- 

 Coll found the same law obtain ; allowing for the difference 

 in shape, and for the flattening of the pipe necessary to 

 form the mouth properly, he considered that the mean 

 depth was about equal to five-sixths the diameter, or— 



6 

 Substituting this in the above equation it becomes, for 

 cylindrical pipes — 



V 3 

 Taking now the mean velocity of sound given by M. 

 Cavailld-Coll, namely, 340 metres or 1 1 15 feet per second ; 

 putting the dimensions of the pipe in inches, and altering 

 f to represent the number oi double vibrations per second, 

 according to our English custom ; we obtain, finally, for 

 cylindrical pipes — ■ 



Z=669°-5^;or 



y_ 20070 



Mr. Ellis's rule is — 



3^ + S^ 

 20080 



V = 



3^ + Si^ 

 the letter V, however, in the denominator being clearly a 

 misprint for D. 



The foregoing rules, it must be stated, apply to pipes 

 open at the end, which constitute the great bulk of those 

 in an organ. William Pole 



GEOGRAPHICAL NOTES 



The letter from Sir Rutherford Alcock in yesterday's 

 Times, announcing the death of Mr. Keith Johnston, will 

 be received with surprise and sincere regret. As our 

 readers know, Mr. Johnston was leading the Geographical 

 Society's expedition from Dar-es-Salaam to the north end 

 of Lake Nyassa, and, if possible, thence to Tanganyika. 

 A start was made on May 14, and now the sad news 

 comes that the young leader died of dysentery on June 28, 

 at Berobero, about 130 miles inland. Mr. Johnston came 

 of a famous geographical house, and had already done 

 good exploring work in South America. He was en- 

 thusiastic on the matter of African exploration, and was 

 well qualified to carry it out in a scientific method. His 

 death is a real loss to scientific geography.' We are glad 

 to learn that the expedition will be continued under the 

 leadership of Mr. Thomson, the geologist who accom- 

 panied Mr. Johnston. 



It is with great pleasure we learn from a letter of Dr. 

 G. Nachtigal to the editor of Petermann's Miithethmgen, 

 that the announcement of Dr. G. Rohlfs' retirement from 

 the leadership of the expedition of the German African 

 Society was premature. He did express a wish to resign, 

 but has since been able to overcome all initiatory diffi- 

 culties, and left Benghazi with his followers on July 4, 

 and it is hoped will be able to reach Abesh, the chief 

 town of Wadai, about the middle of ijext month. Dr. 

 Nachtigal's account of his own great exploring work in 

 North and Central Africa from 1869 to 1874 has just been 

 published in Berlin. 



At the last sitting of the Paris Geographical Society, 

 M. Paul de Soleillet explained his scheme for putting 

 Timbuctu in communication with the Atlantic. A rail- 

 way must be made from Dakkar, on the Atlantic coast 

 and St. Louis, the head city of French Senegal. This 

 work will be begun next winter. The Senegal must be 

 rendered navigable from St. Louis to Bafoulabd, and a 

 canal constnacted from Bafoulabd to Bamakou, on the 

 Niger. These projects having been adopted by the High 

 Commission, the Survey for the canal will begin im- 

 mediately. The Niger is navigable without works of 

 any description from Bamakou to Timbuctu and other 

 places below for a distance of 1,500 miles. The aggre- 

 gate expense required for the whole of the work is esti- 

 mated at a million sterling, and the number of people 

 placed in close connection with French Senegal thirty- 

 seven millions. A M. Fourreau has sent a letter to the 

 President of the Society stating that he, with two friends, 

 had established a farm in Oued Bish, about 150 miles 

 southward of Biskra, in the direction of the intended 

 Transaharian Railway via Biskra. The exploration com- 

 mittee of the Saharan Railway Commission has recom- 

 mended the Government to send out M. Soleillet to visit 

 the unexplored regions between 15° and 25° N. lat. 



Taken as a whole, the August number of the Geo- 

 graphical Society's monthly periodical appears to be the 

 best that has been issued. The papers are Major Serpa 

 Pinto's notes of his journey across Africa ; Mr. McCarthy's 

 "Across China, from Chinkiang to Bhamo;" and the 

 late Capt. R. R. Patterson's notes on Matabeli-land. 

 The map of South Africa, accompanying Major Pinto's 

 notes, is particularly interesting, as it embodies a good 

 deal of original information. The geographical notes are 

 unusually full and varied, and we are glad to observe that 

 greater attention is being paid to this most essential de- 

 partment of a geographical magazine. Since the note on 

 Major Tanner's exploratory visit to Kafiristan was written, 

 news has unfortunately arrived that ill-health i.has com- || 

 pelled that officer to return to India. There is a useful ^I 

 summary of Dorandt's report, published by the Russian 

 Geographical Society, on his astronomical and magnetic 

 observations on the Lower Oxus, and of Mr. Hillier's 

 account of his journey in North China at the beginning 

 of this year. Climatology also claims a place among the 

 notes. The remainder of the number is occupied with a 

 report of the evening meetings, the proceedings of foreign 

 societies, and notes on new books and maps. 



News has just been received at Copenhagen from the 

 scientific expedition which sailed for Greenland in the 

 Ceres on March 29 last. The expedition, which consists 

 of two naval officers, MM. Jansen and R. Hammer, and 

 a student of polytechnics, M. Kornerup, reached the Hol- 

 steinborg Colony, in Greenland, on April 30, and at once 

 proceeded with their investigation and measurement of 

 the coast and fjords between Holsteinborg and Egedes- 

 minde. They left the neighbourhood of Holsteinborg 

 on May 15, travelling in small Greenland boats. From 

 that date to the end of August, when they hope to reach 

 Egedesminde, the explorers will have to camp in their 

 boats or on the rocky shore. However, the summer 

 nights are bright in those latitudes, and the expedition is 

 weU equipped with all necessaries. 



