66 Progress of Invention. 



asunder. The liquid nietal is poured into this, while it is revolving 

 with great rapidity ; and the centrifugal force causes all the interior 

 details of the mould to be perfectly and sharply filled; so that when 

 the metal has cooled, and the mould is removed, a perfectly un dis- 

 torted and smooth casting is obtained. 



Turbine Brush. — This simple but effective contrivance, which 

 has been lately patented in America, consists of a circular brush, at 

 the back of which is a small turbine wheel, supplied with water 

 through the handle by a flexible tube attached to the latter. The 

 rapid revolution of the brush, aided by the supply of water, causes 

 it to act very effectively, while at the same time a perfect uniformity 

 of wear is secured. This ingenious application of the principle of 

 the turbine is another example of the practical nature of American 

 inventions. 



Miller's Heliotrope. — Professor "W. H. Miller, of Trinity Col- 

 lege, Cambridge, has communicated to the Cambridge Philosophical 

 Society an account of a new form of heliotrope, intended to reflect 

 the rays of the sun to any desired distant object by means of the 

 hand and eye alone. In its first form the instrument depends upon 

 the property that a ray of light falling in succession upon three 

 plane mirrors at right angles to one another, returns upon a path 

 opposite and parallel to its original course. If the source of light 

 is the sun, its rays, after falling upon three such mirrors, will be 

 returned back again to itself. At any point of their circuit rays will 

 therefore be found going in exactly opposite directions. Professor 

 Miller avails himself of this property to construct a heliotrope by 

 making one mirror of the three the largest. It is coated with chemically 

 precipitated silver, which sends a large quantity of light directly to 

 the distant object desired to be illuminated. The other two mirrors 

 are small pieces of unsilvered glass fastened at one corner of the 

 larger mirror, so that they are at right angles to each other, and 

 make right angles with two sides of the large mirror. When a 

 ray of light falls on the large mirror, and is reflected in one direc- 

 tion, a second ray parallel to the first falls upon one of the small 

 mirrors, by which it is reflected on the second small mirror, and 

 from thence through an aperture, in the large mirror in a direction 

 parallel, but opposite to that taken by the first ray. This ray being 

 admitted to the eye of the operator through a hole in the silver coat- 

 ing of the large mirror, enables him to direct the principal beam to 

 any distant object, by hand and eye, at pleasure. Two edges of a 

 rectangular looking-glass, if perfectly square and well polished, pro- 

 duce the same effect as the two small mirrors of unsilvered glass. 

 But a tinted glass, to relieve the eye, must be applied at the back of 

 the looking-glass, where the metallic silvering is scratched away. For 

 the signals of a survey this form of heliotrope will probably super- 

 sede all others, from tho ease of its construction, its simplicity in 

 use, and from the impossibility of deranging its adjustments. It i3 

 made and sold by T. E. Butters, 4, Crescent, Belvedere Road. 



Solution of the Aniline Dyes. — Hitherto almost all the aniline 

 dyes and their congeners, bein<j insoluble in water, required for 

 solution alcohol or methyline. The former is objectionable on ac- 



