8o 



SCIENCE. 



[Vol. XVII. No. 418 



his skill and activity largely depends the success of the season. 

 Mahogany-trees do not grow in clumps and clusters, but are 

 scattered promiscuously through the forests, and hidden in a dense 

 growth of underbrush, vines, and creepers. It requires a skilful 

 and experienced woodsman to find them. No one can make any 

 progress in a tropical forest without the aid of a machete, or heavy 

 bush-knife. He has to cut his way step hy step. The mahogany 

 is one of the largest and tallest of trees. The hunter seeks the 

 highest ground, climbs to the top of the highest tree, and surveys 

 the surrounding country. His practised eye detects the mahogany 

 by its peculiar foliage. He counts the trees within the scope of 

 his vision, notes directions and distances, then descends and cuts a 

 narrow trail to each tree, which he carefully marks, especially if 

 there is a rival hunter in the vicinity. The axe-men follow the 

 hunter, and after them go the sawyers and hewers. 



To fell a mahogany-tree is one day's task for two men. On ac- 

 count of the wide spurs which project from the trunk at its base, 

 scaffolds have to be erected and the tree cut off above the spurs, 

 which leaves a stump from ten to fifteen feet high. While the 

 work of felliDg and hewing is in progress, other gangs are em- 

 ployed in making roads and bridges, over which the logs are to be 

 hauled to the river. One wide truck pass, as it is called, is made 

 through the centre of the district occupied by the works, and 

 branch roads are opened from the main avenue to each tree. 



The trucks employed are clumsy and antiquated contrivances. 

 The wheels are of solid wood, made by sawing off the end of a 

 log and fitting iron boxes in the centre. The oxen which draw 

 these trucks are fed on the leaves and twigs of the bread nut tree, 

 which gives them more strength and power of endurance than 

 any other obtainable food. Mahogany-trees give each from two 

 to five logs ten to eighteen feet long, and from twenty to forty- 

 four inches in diameter after being hewed. The trucking is done 

 in the dry season, and the logs collected on the bank of the river, 

 and made ready for the floods, which occur on the largest rivers 

 in June and July, and on all in October and'November. The logs 

 are turned adrift loose, and caught by booms. Indians and Caribs 

 follow the logs down the river to release those which are caught 

 by fallen trees or other obstacles in the river. 



The manufacturing process consists in sawing off the log-ends 

 which have beeen bruised and splintered by rocks in the transit 

 down the river, and in re-lining and re-hewing the logs by skilful 

 workmen, who give them a smooth and even surface. The logs 

 are then measured, rolled back into the water at the mouth of the 

 river, and made into rafts to be taken to the vessel, which is 

 anchored outside the bar. The building of sloops and small 

 schooners for the coasting trade is an important industry in the 

 island. The frames of such vessels are made of mahogany, Santa 

 Maria, and other native woods of well-tested durability, and proof 

 against the ravages of worms, which abound in the waters. 



At present the only woods exported from Honduras are mahog- 

 any and cedar wood, although the forests abound in other 

 varieties, which Consul Burchard states are quite as useful and 

 ornamental, and which must eventually become known in foreign 

 markets, and open " new and inviting fields for industry and 

 trade." 



CANADIAN SOCIETY OF CIVIL ENGINEERS. 



The fifth annual meeting of the Canadian Society of Civil En- 

 gineers was held in Montreal on Jan. 15, when Col. Sir Casimir 

 Gzowski, A.D.C., was re-elected president for the third time. In 

 consequence of ill health he was unable to deliver the usual set 

 address, but in a short speech he congratulated the society upon 

 the continued and steady progress which it was making, stating 

 that it already occupied a position which its sister society in the 

 United States had not reached in the first decade of its exist- 

 ence. 



The total number on the list now includes 633 members, asso- 

 ciates, and students, and many original papers of engineering 

 value have already been printed. It was also announced that the 

 president had endowed a silver medal to be awarded annually for 

 the best paper submitted during the year, provided such paper 

 shall be adjudged of sufficient merit as a contribution to the 

 literature of the professionof civil engineering. The first of these 



medals has been awarded to Mr. E. Vautelet for his paper on 

 "Bridge Strains." 



During the past year the society has moved from the rooms 

 generously lent by the University of McGill College to more com- 

 modious quarters specially fitted up for their accommodation, and 

 centrally located on St. Catherines Street, near the Windsor 

 Hotel. 



The principal papers discussed by the society during the past 

 year are the following: " The Screening of Soft- Coal," by J. S. 

 McLennan; "The Manufacture of Natural Cement," by M. J. 

 Butler; "Columns," by C. F. Pindlay; "Irrigation in British 

 Columbia," by E. Mohun; "The Sault Ste. Marie Bridge," by G. 

 H. Massy; "Generation and Distribution of Electricity for Light 

 and Power," by A. J. Lawson; "Developments in Telegraphy," 

 by D. H. Keeley; " Errors of Levels and Levelling," Parts 1 and 

 3, by Professor C. H. McLeod. 



LETTERS TO THE EDITOR. 



*** Correspondents are requested to he as brief as possible. The writer^ a name 

 is in all cases required as proof of good faith. 



The editor loill be glad to publish any queries consonant with the character 

 of the journal. 



On request, twenty copies of the number containing his communication will 

 be furnished free to any correspondent. 



Rain Formation. 



It will probably be readily admitted that one of the most com- 

 plex problems in meteorology is the explanation of the condensa- 

 tion of vapor into visible drops. Cloud has been formed in a 

 receiver by cooling saturated air very rapidly, but it is doubtful 

 whether actual raindrops have been formed artificially. One of 

 the most serious difficulties encountered in studying the problem 

 has been the fact that our observations have been made mostly 

 several thousand feet below the point of formation of the rain- 

 drop. Observations on mountain tops have shown a great in- 

 crease in precipitation above that at the base; for example, the 

 rainfall on Mount Washington (6,379 feet) is double that at Port- 

 land, Me. , though the latter station is on the seacoast. In Sep- 

 tember, 1880, the precipitation was 15.33 inches and 3.30 inches, 

 and for the year ending June 30, 1880, 97.10 inches and 45.03 

 inches, at the two stations respectively. An explanation of this 

 apparent anomaly might aid in solving the general problem before 

 us. 



It has been held by some that the rocks and earth at the top of 

 the mountain are colder than the air which blows over it, and for 

 this reason there is the greater condensation at the summit ; but 

 it has been proved that the rocks on Mount Washington are sev- 

 eral degrees warmer than the air, so that this explanation will 

 not hold. Others have thought that warm saturated air, as it is 

 forced up the side of the mountain, is very much cooled by ex- 

 pansion, and this cooling produces the increased precipitation. 

 This does not hold, however, in the case of Mount Washington, 

 because the top rises up like a sharp cone, and the increased rain- 

 fall covers an area many times greater th^n can possibly be af- 

 fected in this way. I think it will be admitted that a large share 

 of the precipitation on our mountains is formed within a few hun- 

 dred feet of the top, in a vertical direction. If so, it would 

 seem that we have here a most excellent opportunity for studying 

 this problem. 



There have been published recently, by Harvard College, a com- 

 plete set of the observations made by the Signal Office at Pike's 

 Peak (14,134 feet), from 1874 to June, 1888, and these are now in 

 a most convenient form for study. It has occurred to me that a 

 valuable addition to our knowledge of the conditions under which 

 precipitation occurs might be made by studying the connection, 

 if any existed, between the temperature fluctuations and precipi- 

 tation at this elevated point. The usual view is, that a column 

 of saturated air in which moisture is forming into drops or snow- 

 flakes is warmer than the air all about at the same level, and for 

 this reason it has a tendency upward. W6 may put this in an- 

 other form: if we pass into a column of air in which rain is fall- 

 ing, we shall find the temperature steadily increasing from the 

 circumference to the centre ; or, if we take the second interpreta- 

 tion just given for the increased rainfall at the summit of a 



