The Heat-Ray is the Martians' primary offensive weapon.
The Heat Ray is described as a camera-type box with a circular mirror attached to one of the Tripod's tentacles.
It was the first device to be set up and made operational when the Martians arrived on earth, and is therefore probably capable of being detached, and operated separately from a fighting machine if needed, although the two are always shown together after the first fighting machine appears.
The effect of the ray is as follows:
"Then it was as if an invisible yet intensely heated finger were drawn through the heather between me and the Martians, and all along a curving line beyond the sand pits the dark ground smoked and crackled".
The Heat Ray is also described as "A generator of intense heat in a chamber of practically absolute non-conductivity. This intense heat they project in a parallel beam against any object they choose, by means of a polished parabolic mirror of unknown composition, much as the parabolic mirror of a lighthouse projects a beam of light.".
The only visible element of the ray in the book is a bright white flash emitted from the box chamber while the ray is fired. This is usualy changed for other media, which often shows the heat ray been visible like a beam of coloured light. The colour of the heat ray's light varies from adaptation to adaptation, with colours including red, green, white, yellow and blue.
In the 1953 George Pal adaptation, the Martians used 2 types of weapons. The primary is a Disintegration Heat Ray. It is mounted on a flexible turret known by some as a swan or cobra-neck. This weapon leaves of its victims nothing but remains a charred shadow of where they once stood.
The other weapon is a "Skeleton beam" (due to their ability to create a X-Ray effect upon hitting their human target) equipped on both sides of the Martians Wingtips. In the film its effect is explained as neutralizing Mesons, the atomic glue holding matter together, By cutting across their lines of magnetic force, any object will simply cease to exist.
In Steven Spielberg's 2005 movie, the heat-ray was a blueish-white arc of light that turns its victim into dust and leaves their clothes intact yet destroys and burns everything else like typical laser weaponry heat-ray associated with. The reason of this is the heat-ray appears to be a high energy coherent emission of microwaves not unlike Maser that causes the water in the human body to superheat into very high temperature steam, which then causes the victim to explode into ash as it instantly expands. The emitters are portrayed by two crescent shaped "arms" on the tripod's head.
In War of the Worlds: Goliath, heat-rays are green (for martians) or red (for A.R.E.S.) laser beams that strip people down to the bone, or cause machines to explode.