ON THE CRYSTALLINE SLAGS. 351 
-may perhaps not be wholly eliminated at even 20 or 24 inches distance. 
Perhaps no better mode of experiment on this peculiar transportation of the 
_ atmosphere by railway trains could be devised than the trial of its cooling 
_ power. In the first of the above experiments the air-displacement appeared 
to be about 13 miles an hour at 3 inches from the carriage ; about 24 miles 
_ at 18 inches, and 30 miles at 24 inches. 
The result now arrived at must, however, be regarded as only a first ap- 
proximation, and requires to be tested and corrected by more rigorous pro- 
cesses. For this purpose the cooling of the wet bulb has been observed 
when carried round by a lathe movement, and when subject to the vibrations 
of a pendulum. The results are yet incomplete, but may be offered for the 
consideration of the Association on a future occasion. 
Report on the Crystalline Slags. By Joun Percy, M.D. 
_ We have pleasure in now presenting to the Association the results of our 
investigation of the crystalline slags. It is obvious that such an investiga- 
_ tion must be limited by the opportunity of obtaining specimens, which re- 
quire to be diligently sought for at the various metallurgical works; and 
that, consequently, it is impossible for us at present to offer anything like a 
complete report upon this interesting subject. We have however been for- 
tunate in procuring already an extensive series of beautifully crystallized 
slags, several of which we have not yet had time to examine. We are espe- 
cially indebted to Mr. John Dawes, of West Bromwich, and to Messrs. 
Blackwell and Twamley, of Dudley, for many valuable contributions. In 
_ the present Report we have confined our attention to the slags produced in 
_ the smelting and manufacture of iron. We shall adopt the following ar- 
rangement :— 
1. The crystallographic and mineralogical description by Professor Miller. 
2. The analysis*. 
3. Special remarks. 
The first series is composed of six specimens. Nos. 1 and 2 were ob- 
tained from hot-blast furnaces in the vicinity of Dudley ; Nos. 3 and 4 from 
_ Messrs. Blackwell's hot-blast furnaces at Russell’s-hall, near Dudley; No. 4 
_ from one of Mr. Philip Williams’s cold-blast furnaces, at the Wednesbury 
_ Oak Works, near Tipton; No.6 was brought by Mr. Samuel Blackwell from 
a hot-blast furnace named La Providence, at Marchienne, Charleroi, Bel- 
‘gium. No. 3 was produced when the furnace was considered to be work- 
ing unsatisfactorily, from some interruption to the free course of the blast. 
The crystals of the slag No. 3 are square prisms, terminated by planes 
perpendicular to the axis of the prism. Many of the prisms have their 
angles truncated by planes, making equal angles with the adjacent faces of 
the prism. 
Al ., Specific gravity of slag | 
Hardness = 6. At 19°1 specific gravity of water =2°9242. 
_ _ The crystals of slag No. 4 are square prisms, having the angles truncated 
like No. 3. 
Hardness = 5°5. At 18°-2 C Ue? Beno OF SIRS eat) oF sins, 
specific gravity of water 
* Tam happy to state that I have had the assistance of my friend Mr. David Forbes, 
_ brother of Professor Edward Forbes. To the analyses made by myself I shall append my 
_ Own initials, and to those made by Mr. Forbes the initials of that gentleman. 
=2'9187. 
