Makch 2, 1883.] 



SCIENCE. 



107 



are subjected. He took up these processes iu their 

 order, and gave the results of a close and careful 

 study into the matter. In the operations of punch- 

 ing and shearing, it is conceded that the effect is to 

 liarden the metal to a local extent only; and also 

 that enlargement of the area punched by i-eaming 

 restores the plate to its original state. But Mr. Hill 

 did not agree with Lieut. Barber, who has announced, 

 as the result of his i-esearches, that the amount of 

 enlargement is a fixed quantity: on the contrary, the 

 amount is dependent upon the carbon percentage and 

 the thickness of the plate. The experiments wei-e 

 made with plates 18 inches wide, Xi ^; 3-"tl }i inches 

 in thickness, and .30, .40, and .50% carbon. They were 

 cut in the planer, cross\i^ise to the direction of the fibre ; 

 and three pieces from each plate were taken — one 

 from the centre, and one from each end — for exami- 

 nation. The result of the exijeriments led to the con- 

 clusion, that the heavier the plate, or the lower the 

 carbon percentage, the greater the effect of punch- 

 ing. Here is a clear indication of the direction which 

 must be given to this line of investigation ; but the 

 conclusion is evident, that a restoration of strength 

 is effected by reaming, although the enlargement is 

 not a fixed quantity. In the cases of sheared and 

 hammered open-hearth steel plates, annealing always 

 restores the plate to its original strength. The capa- 

 citv for welding is in inverse ratio to the carbon per-, 

 centage, and the metal must not be heated any higher 

 than is absolutely necessary to effect the weld. An- 

 nealing should immediately follow the welding, and 

 the metal must be carried to a higher temperature 

 than when it was last worked. It is a most impor- 

 tant operation, and its effect varies directly with the 

 carbon percentage. A metal bath gives unsatisfac- 

 tory results: the best are obtained by annealing with 

 oil. There is no more danger to be apprehended in 

 annealing steel than in performing the same opera- 

 tion on iron; and nearly all trouble can be traced to 

 poor workmanship. 



The strength of American woods. 



BY PKOF. S. P. SHAEPLES OF CAMBRIDGE. 



When Gen. Walker was put in charge of the Cen- 

 sus department, he was authorized to appoint experts 

 to inquire into special industries. Under this act 

 Prof. Charles S. Sargent of Brookline was appointed 

 to gather statistics in relation to forest industries. 

 Soon after his appointment, in 1869, he became con- 

 vinced that it would be desirable to make an exami- 

 nation of the fuel-value of the various woods of the 

 United States ; and this work was placed in my hands. 

 At the same time I made the suggestion, that, while 

 we had the opportunity, it would be well to test also 

 the strength of these woods: the suggestion was at 

 once adopted, and Professor Sargent immediately set 

 his agents at work in various parts of the country to 

 collect specimens of all the trees growing in their 

 localities; employing, as a rule, botanists who were 

 familiar with the flora of the region in which they 

 were at work. The result was the collection of over 

 1,300 specimens of wood, comprising more than 400 

 species and varieties, nearly 100 of which had not 

 before been described as trees growing in the United 

 States. The ash and specific gravity of every speci- 

 men in this collection have been determined, in most 

 cases in duplicate: there have been about 2,600. ash 

 and 2,800 specific-gravity determinations. About 325 

 species were further tested for transverse strength 

 and resistance to crushing. In these series about 

 1,300 specimens were tested; and, as each was tried 

 in three diSerent ways, it made in all about 3,900 



tests. There was a total of about 10,600 tests made 

 on the specimens, many of them being of a series 

 that required at least ten entries on the final report. 

 In addition, seventy tests were made of the carbon 

 and hydrogen in a number of the specimens. These 

 tests iiave already, so far as the results of the ash 

 and specific gravity of the dry wood are concerned, 

 been published {Forestry bull., No. 32); and a bulle- 

 tin is soon to be published giving the deflections 

 under various loads. 



After the wood had become thoroughly seasoned, 

 it was dressed out into rods 4 centimetres square 

 and 11 decimetres long. These were tested on the 

 Watertowii machine, the stick being placed in a per- 

 pendicular postion, resting on supports that were 

 exactly one metre apart; the deflection being meas- 

 ured by an ordinary Brown and Sharp's scale gradu- 

 ated to millimetres. The force was applied at the 

 centre of the length, by means of an iron bearing 

 with a diameter of 12.5 millimetres. The loads were 

 applied 50 kilogrammes at a time, and the deflection 

 read on the scale after each weight was added. When 

 the weight equalled 200 kilos, the load was taken off, 

 and the set was measured; the load was again put 

 on, the reading taken at 200 kilos, and again at every 

 50 kilos imtil the stick was broken, the breaking- 

 weight being also noted. In entering the test, a 

 record was made of the direction of the fibre in each 

 piece, — i.e., whether the pressure was applied parallel 

 with, or perpendicular to, the annual rings, or quar- 

 tering them, — but this portion of the test resulted in 

 a failure, the wood seeming to have equal strength 

 in all directions of application of pressure. The 

 stick was also weighed to about half a gramme, from 

 which was calculated the specific gravity. To deter- 

 mine the specific gravity exactly, blocks were taken, 

 carefully dressed out to precisely 11 centimetres in 

 length and 35 millimetres square. They were care- 

 fully dried at the temperature of boiling water for a 

 week, and were then measured with a micrometer 

 caliper, and weighed ; the specific gravity being calcu- 

 lated from the measurement and weight. 



The ash was determined by igniting small blocks, 

 thirty-five millimetres square and a centimetre long, 

 dried in the same way, in a platinum dish in a muffle 

 furnace heated by gas, the heat being applied so care- 

 fully that in most cases the ash retained the exact 

 shape of the block: by taking care not to melt the 

 ash, there was avoided a common error resulting from 

 the non-combustion of a portion of the carbon. The 

 ash was perfectly white, except where manganese or 

 iron was present in the w^ood. It was judged best 

 to report the ash exactly as found, and not to attempt 

 any correction on account of carbon dioxide that 

 might have been lost from the calcic carbonate pres- 

 ent. From the results of the specific gravity and 

 ash, the approximate full value was calculated. 

 Count Eumford made experiments from which he 

 came to the conclusion that the same weight of all 

 woods will give the same amount of heat when 

 burned under the same conditions ; and Marcus Bull 

 of Philadelphia, in 1826, reached the same result. 

 These are the only attempts known to determine the 

 fuel-value of wood. It is evident, that, if the cellu- 

 lose in all woods is of equal value, that with the most 

 ash is of the least value for fuel. 



In 1848 Liebig made determinations of the carbon 

 and hydrogen in the average composition of Euro- 

 pean woods; and, singularly enough, all of his experi- 

 ments were made on hard wood, with one exception, 

 that of fir. I determined the carbon and hydrogen 

 in forty specimens of hard, and twenty-nine speci- 

 mens of soft, wood. The average results agreed 



