SCIENTIFIC SUMMARY. 
207 
PHYSICS. 
Sensitive Flames . — A new form of burner for tbe production of sensitive 
flames is described by Mr. R. H. Ridout (“Nature,” xv. 119). It bas the 
advantage of giving a very sensitive flame at very low pressures. It con- 
sists of a glass or metal tube about five inches long and five-eighths of an inch 
in diameter, closed at one end by a perforated cork, through which slides a 
piece of glass tube one-eighth of an inch in diameter, and about six inches 
long. One end of the smaller tube is drawn out in the blow-pipe to form 
a jet with an aperture of about ~ inch; the other end is connected with 
the supply of gas. The larger tube being then fixed in a support, the 
smaller one is pushed up into it through the perforated cork, until the jet 
aperture is nearly level with the mouth of the larger tube ; and on a light 
being applied, it gives a long steady flame, which is rendered sensitive by 
lowering the smaller tube. 
By an ingenious arrangement the same gentleman has arrived at some 
interesting results with regard to the influence of combustion on the pres- 
sure of gas in tubes. Two parallel vertical tubes are connected by a 
horizontal tube containing a drop of water as an index of pressure. When 
gas is allowed to flow through both tubes, and one of the jets is lighted, 
the water moves towards the other, showing that the effect of the combus- 
tion is to obstruct the flow. A sensitive flame was found to produce greater 
resistance when shortened by a noise or a musical note, but this effect is 
produced even when the jet is not lighted. 
Singing Tubes. — M. A. G. Montenot lately exhibited to the French Society 
for the Encouragement of Industrial Arts some experiments on metallic 
tubes which produce sounds when a source of heat is placed within them in 
a particular nodal position. A copper tube, into which a piece of metallic web, 
heated to redness, was introduced, produced an intense sound. Into another 
tube a little furnace, containing incandescent charcoal, was put, and this 
also produced a musical sound, which was modified according to the position 
occupied in the tube by the source of heat, and the length of the tube. M. 
Montenot regards this experiment as particularly interesting, not only from a 
theoretical point of view, as introducing a new element into the investigation 
of the cause of the sound produced by singing flames, but also because it may 
admit of industrial application in the production of sounds of sufficient 
intensity to be heard at great distances, as fog-signals on dangerous coasts. — 
Les Mondes , February 15, 1877. i < 
A Gigantic Induction Coil. — Mr. Apps has lately constructed for Mr. W. 
Spottiswoode the largest induction coil yet made. It is described by Mr. 
Spottiswoode in the “ Philosophical Magazine ” for January. It has two pri- 
maries. That used for long sparks has a core consisting of a bundle of iron 
wires *032 inch thick, which form a solid cylinder 44 inches long, and 3-5625 
inches in diameter, and weighing 67 pounds. The copper wire of this primary 
is 660 yards long, and *096 inch thick ; it has a conductivity of -93, and a total 
resistance of 2-3 ohms. It contains 1,344 turns, wound singly in six layers ; 
its total length is 42 inches, its internal diameter 3-75 inches, and its ex- 
ternal diameter 4-75 inches. The second primary, to be used with batteries 
of less resistance for short thick sparks, and for spectroscopic purposes, has 
