THE TECHNOLOGIST. [March 1, 1864 



366 ON A MEANS OF RENDERING OSTENSIBLE 



form to equal quantities in weight of the different sorts of wood, we 

 shall have proportionate visible representations to the specific weights of 

 the wood. We can thus at the same time have spheres of more or less 

 volume when we shall have given that shape to the same weight of dif- 

 ferent woods. We can also vary the experiment by giving the form of a 

 cube, a cylinder, or of a prism ; but it may be remarked that the first- 

 named presents the greatest difficulty, as in shaping it the small 

 fractions of weight cannot well be accurately shown ; the cylinder or 

 prism form will be found better suited to our object, those differences 

 coming more together on one side, the height. I give the preference to 

 the prisin with a square base, but the difficulty often of finding woods 

 of a certain thickness, leads me to adopt the prism with rectangular base ; 

 and this is the shape in which was prepared the collection of woods I 

 showed at the International Exhibition of 1862, in the Italian Depart- 

 ment.* The different sorts of wood, having been conveniently dried, are 

 disposed in parallel opipedes of an indefinite length, two centimetres 

 thick by five centimetres broad, and from each is forthwith cut the 

 necessary length to represent 200 grammes of weight. In this manner we 

 obtain a series of prisms, which are as long as the wood from which 

 they were formed. Disposing them naturally as I did, from the lowest 

 to the highest, we could obtain immediately a curve of which the 

 " ordonn6es" are inversely proportioned to the density of the wood's 

 weight by the air. 



I will now give the heights, which I have measured in centimetres, 

 and by means, of which may be retraced the curve obtained with those 

 woods I had at my disposal. 



Table op the Specific Weights of different Woods, indicated 



BY THE LENGTH OF A PaRALLELOPIPEDE OF TWO CENTIMETRES THICK 



AND FIVE CENTIMETRES BROAD, WEIGHING 200 GRAMMES. 



Length in 

 Centimetres. 

 Epaw, a species of Ebony from America . . .150 



Catayba of Paraguay 170 



Medicago arborea of Sardinia 170 



Quebracho of Paraguay, resembling an Acacia, probably 



A. tenuifolia 173 



Amaranth, or violet wood, Palo morado of Paraguay, 



probably a Copaifera 185 



Kose or tulip wood (Liriodendron tulipiferd) . . 185 



Brazil wood (Ccesaljrinia echinata?) .... 186 



Hawthorn, Aubepine, or Bossolo (Cratagus pyracanthus) 187 

 Logwood (Hccmatoxylon campechicmum) . . . 190 



Olive {Oka Europea) 193 



Lignite, or Fossil wood of Lango, in Piedmont . . 200 



* This collection was formed and shaped in 1860, at the Technical Institute, 

 Turin. 



