8 



HARDWICKKS SCIENCE-GOSSIP. 



" solid flames," an awkward name, inasmuch as a 

 gaseous fluid is not a solid. " Solid," when applied 

 to a flame, merely means not hollow. 



Petroleum Vapour Fuel. — Another kind of gas 

 is similarly used. This is the vapour of a volatile 

 distillate of petroleum, that which is too volatile to 

 be safely used in ordinary lamps, and which bears 

 the commercial names of gasoline, benzoline, &c. 



The vapour is obtained by simply passing air 

 through the liquid, the air thus becomes saturated 

 with the vapour, and supplies the oxygen necessary 

 for its combustion. As the volatile liquid the " pe- 

 troleum spirit " is almost a waste product, has at 

 times been burned in the open air to get rid of it, 

 fuel of this kind is cheap enough in petroleum- 

 yielding regions, such as Pennsylvania and Baku, &c. 

 The steam packets of the Caspian are now regularly 

 supplied with petroleum furnaces, where either the 

 vapour is burned in this manner, or jets of the liquid 

 hydro-carbon itself are mixed with air, and thrown in 

 blaze upon the boilers. Attempts have been made to 

 introduce it in this country, but they have failed 

 simply because here it costs more than coal. The 

 cost of carriage from the American wells is about 



(part of a cigar box), a little larger than an ordinary 

 slide, and made a hole three-quarters of an inch 

 square in the middle of it. About half an inch from 

 either end, on what I intended to be the lower side, I 

 cut a narrower transverse groove, and then slipptd an 

 indiarubber band over each end until it reached the 

 groove. I then took the slide I wanted to examine 

 and placed it on the wooden one under the elastic 

 rings, then, by inserting a wedge between the wooden 

 and other slide at the proper part, the object can 

 be placed as desired. This little device is also useful 

 in enabling one to see portions of an object which 

 one would not otherwise be able to do. 



I devised a very simple contrivance for placing an 

 unmounted object in any desired position on the 

 stage of a microscope. It will effect more when 

 placed on a rotating stage than Messrs. Beck's little 

 mechanism, which I think they call " a rotating disc 



Fig. 3. — Apparatus for Microscopical Drawing. 



Fig. 4.— Apparatus for placing Unmounted Objects on Stage. 



sixpence per gallon — or £6 per ton. One ton of oil 

 does the work of about i* to 15 tons of coal. Some 

 have claimed double, but this is questionable. 



In time of naval war it may possibly supersede coal 

 for some purposes, as steam may be got up more 

 rapidly with a petroleum furnace than with coal. 



ACCESSORIES FOR MICROSCOPICAL 

 DRAWING. 



IT has often happened to me (and I expect many 

 persons have experienced the same difficulty), 

 when wishing to draw a mounted object under the 

 microscope that the object was not placed exactly in 

 the position in which one wishes to draw it, and to 

 so place it, the slide requires raising at one end or 

 side. I knew of no apparatus for effecting this when 

 the object was a transparent one, and lately, when 

 making some drawing with a camera, I was much 

 bothered by some of the objects not being quite 

 truly placed. After a little consideration, I devised a 

 very simple little piece of apparatus which effects my 

 purpose admirably, which I will describe, as others 

 may also find it useful. I cut a piece of thin wood 



holder," and at only a quarter of the price : it is 

 difficult to describe it accurately, but the figure 

 shows its action. By turning the milled head the 

 object can be moved in a direction transverse to the 

 apparatus, and by moving the other hand in or out, the 

 object can be moved in a longitudinal direction. If to 

 these movements be added that given by isolating 

 stage, the object can be viewed in any aspect without 

 removing it from the instrument. The hole in the 

 vertical tube can be fitted with a cork to hold pins ; a 

 small pair of forceps or a piece of wax can be used to 

 hold a geological specimen. Messrs. Baker & Co., 

 243 High Holborn, are the makers of this object 

 holder, for which they charge $ s - x have used this 

 instrument a great deal, and I find it is most useful, 

 and that it works in a very satisfactory manner. 



G. S. S. 

 Tanbridge Wells. 



Telephonic communication has been established 

 between Paris and Rheims, a distance of 172 kilo- 

 metres. The ordinary telegraph-wire is utilised for 

 the purpose. The tariff is one franc for five minutes' 

 conversation. 



