Material for the lenticular lens, and consequently of making a fire, can also serve ice if it is sufficiently transparent. The ice, breaking the beams itself is not heated and does not melt. The refractive index of ice is only slightly less than that of water, and if, as we have seen, it is possible to make fire using a balloon filled with water, it is possible to do this with lentils from ice.
Ice lentils rendered good service in Jules-vernova “the Journey of captain Hatteras”. Dr. Clawbonny in the manner that the fire was lit, when they had lost the flint and found myself without fire, in the terrible frost in 48 degrees.
- “This is a misfortune, " said Hatteras doctor.
"Yes, " replied the man.
- We do not even have a telescope, with which we could remove the lentils and the fire.
"I know, " replied the doctor, " and it is a pity that there is no: the sun's rays are strong enough to ignite tinder.
- What to do, have to satisfy the hunger of raw bear meat, " said Hatteras.
"Yes, " murmured the doctor, " at least. But why wouldn't we...
What you have in mind? - asked Hatteras.
- I came up with the idea...
- Thought? - exclaimed the boatswain. - If you got the idea, then, we are saved!
I don't know how will - ranged doctor.
"What have you invented? asked Hatteras.
We don't have lentils, but we will make.
- How? "asked the boatswain.
- Otchipwe from a piece of ice.
'Do you think...
- Why not? After all, it is only necessary that the rays of the Sun were reduced to one point, and for this purpose the ice can replace the best crystal. Only I would have preferred a piece of freshwater ice: he is stronger and more transparent.
- Now, if I'm not mistaken, this ice block, " said the boatswain on the ice a hundred steps from travelers - judging by its color, is just what you need.
- You are right. Get out your axe. Come my friends.
The three of them went to this ice block Indeed, the ice was freshwater.
The doctor told me to cut off a piece of ice that has a foot in diameter, and began to obravnavati his axe. Then I trimmed it with a knife, finally gradually polished by hand. Turned transparent lentils, as if from the finest crystal. The sun was quite bright. The doctor put the lentils its rays and focuses them on the tinder. After a few seconds, the tinder caught fire”.
“Dr. concentrated rays of the Sun on the tinder”.
The story of Jules Verne's not quite fantastic: the experiences of ignition tree with ice lentils, first successfully performed in England with a very large lentils in 1763, since repeatedly carried out with complete success. Of course, it is difficult to produce transparent ice lentils with the help of such tools as an axe, a knife and “just a hand” (at 48 ° C weather!), but you can make ice lentils easier to pour water into the Cup proper form and freeze, and then slightly heated Cup, remove it from the finished lens.
“Cup for making ice lentils.
Making a similar experience, do not forget that it is possible only in a clear frosty day and outdoors, but not in the room behind the window glass: glass absorbs a considerable part of the energy of sunlight and the remaining is not enough to cause significant heating.