( 83 ) 



water poured in. This would shorten the work considerably, but there are some drawbacks 

 in its use. The weight of the water may vary according to its purity or impurity, and as the 

 flask itself would be of large size, it may suffer from rough use and disarrange the accuracy 

 of the weights indicated on it. 



The manner in which tlie wood-tester should be used is simple. The staff is inserted as 

 shown in the sketch ; the weights are applied with the right hand, while the left steadily 

 holds the l|andle of the wlieel. Tlie downwai-d pressure of the inner toothed body of the 

 quadrant should be attentively watched, and its motion arrested as quickly as possible,* the 

 moment the staff sliews signs of breaking. Tlie scale of -io degreesf on tlie quadrant gives 

 the degree of flexibility, while the weights appended shew the breaking weight. 



2. The pendant wood-tcder is represented in fig IV. It is easier to handle during the 

 process of testing, but its defect is that the elasticity and breaking weight of the staff cannot 

 be tested with the same degree of accuracy as with the quadrant wood-tester ; for it is clear 

 that a wood-staff with a flexibility of 45 degrees will escape from the rest poles as soon as the 

 bend exceeds the dfiimeter of the space between the two poles. The construction scarcely 

 requires any explanation. A brass moveable toothed bar (a) fastened with a clasp {b) to the 

 middle of tlie wood-staff, which is laid horizontally, plays downwards between two tootlied 

 wheels (c and c), of which the teeth of the left wheel play again into the teeth of a smaller 

 wheel, which is held with the left hand by means of a rotatory handle by which the down- 

 ward-movement may be arrested at the moment the testing staff breaks. To ensure the accurate 

 movement of the pendulous toothed and scaled bar, it is made to play through two clamps at 

 m m, a section of one of which is given in fig. IV. No. 2. 



The weights etc. remain the .same as in the quadrant wood-tester. The dimensions of 

 the box itself, on which the construction rests, are, however, much smaller, say about one foot 

 long by half a foot broad and deep. 



The specific gravity and weight of a cubic foot of the wood under test may be ascertain- 

 ed by the use of balance scales, which may be either on the patent lev^er principle, or of ,any 

 other construction that may be preferred. As has already beeu remarked, the 5 testing sticks 

 would be equal to -j'stli or ^^tii of a cubic foot according to the square adopted, and therefore the 

 same experimental staffs cau be used for this purpose either before or after they have beea 

 subjected to the test, and the ascertained weight has only to be multiplied by 20 or 10, 

 in order to give the actual weight of a cubic foot. Only perfectly dry woods should be 

 weighted, for woods are often very hygroscopic, and hence are heavier in a damp than in a 

 dry atmosphere. 



A knowledge of the degree of expansion which timber undergoes during the rainy sea- 

 son, or when otherwise exposed to wet, is of great practical importance. It would not, there- 

 fore, be out of place co try experiments in this direction also, and for this purpose I have 

 devised a wood-expander. 



The wood-exp inder, fig. III., consists of a narrow enameled iron vessel, about \\ feet long 

 by \\ inches deep and wide, to tlie bottom of which are fixed 3 clamps {ana). The central one 

 ought to be three plated, J and the upper part of all three should be made to close and open by 

 means of a hinge, so tliat the wood-staff may be properly inserted. It would also be a 

 much better plan not to allow the staff to rest at all at tUe bottom of the vessel, but to insert it 

 in the manner shewn in No. 2 of fig. III. A cap (6) terminating in a nee He (indicator) is 

 fixed to the end of the staff, and the indicator will play along a brass scale (c). As tlie wood 

 therefore expands, it will move the cap and needle, which will indicate the degree of expansion 

 iu millimetres, or such otner measure as it may be found convenient to adopt in the scale. 



The experimental wood-staff should be cut transversely, and not longitudinally, and 

 should be inserted into the clamps w\i\\e perfectly dry. Experiments of this kind could, there- 

 fore, hardly be carried out in India during the rainy season, but would have to be done 

 during tlie hot dry season, or the experimental staff woald hive to be subjected to artificial 

 heat until perfectly dry. The water must be very carefully poured into the vessel ; so as not 

 to disarrange the position of the wood, and should lieat be required for the experimeut, to 

 produce expansion iu warm water,iS tlie two bricks at d d and the three lamps e e e might be 

 used. Fig. III. No. 3, shews the vessel as seen from above. ^ 



* In order to prevent the wheel snapping backwards, it might be well to hare the projecting nut of the wheel 

 (y) constructed on the prhiciple of a ratchet-wheel (aj (see Fig. IV. No. 3), with a catch which would fit into 

 the teeth ol' the wlieel. 



t In fig II. only 18 degrees have by mistake been indicated, but there ought to be 45 degrees, each of which 

 be divided again into 5 or lu equal portions, if really required. 



J This is done to enable wood-statfs of shorter length (say only half a foot) to be fixed to the middle-clamp, 

 in pliice of the clamp at the extreme end. The degree of expansion in this case would, of course, have to be 

 doubled so as to make tlie results conform to the normal length of one foot. 



At such a temperature as tlie logs would experience in tropical climates if exposed to the sun after a 

 fall of rain, forcontriictioii and expansion very rapidly take place according to the more or less sudden down-pour 

 of rain, alteruatiiig with sun-shiue. 



