Short version: Most palms have no clear sun line. It is a thin vertical crease climbing toward your ring finger, and if you have to squint to find it, you do not have one. William Benham, a palmist writing in 1900, called it incorrect to read its absence as bad luck.
Everything quoted below comes from 41 public domain palmistry books (1879 to 1925) that Alma, our AI palm reader, reads against. If you have ever started a drawing course, a guitar and a pottery wheel in the same year, one of them has a sentence for you, further down. First, your hand.
The ten second check
Hold your hand flat, palm up, in good light, and look for one crease. It starts low on the palm, near the wrist on the pinky side, and runs up toward the base of your ring finger. The picture below shows the route.
If you see a single clear line on that route, that is a sun line. If you see a scatter of short creases, a faint line drifting sideways, or nothing, you do not have a clear one, and you are in the majority.
Two old authors help with what counts. Eveline Farwell's 1898 glossary describes the route:
"Line running upwards from the Mount of the Moon, or centre of the hand, towards the third finger, at the root of which the Mount of Apollo is found."
In plain terms, the "third finger" is the ring finger, and the Mount of Apollo is the pad of flesh under it. You do not need the other names. The Mount of Venus at the base of your thumb is on the other side of the palm, nowhere near it. Benham gave a rule for spotting a real one:
"the general direction of the line itself must be from the Mount of Moon to the Mount of Apollo."
Every palm is full of small creases, so the rule matters. Benham says the line may deflect a little, stop, or throw out branches. What it cannot do is run in some other direction and still count. A short scratch on the ring finger pad fails the test. So does a faint line that drifts sideways. Robert Allen Campbell, writing in 1879, wanted a good one to look like this:
"A favorable line is straight, clearly drawn, fairly colored, of medium size, and continues without breaks"
Which hand to check
Check both, then lean on the left one for what you were born with. Phanos, in 1903, put it as a saying:
"In reading the hand, it must be remembered that the left is the hand we are born with, the right is the hand we make."
If one hand has a faint mark on the route and the other has nothing, it comes down to the route test above. A faint mark that runs the right way is a faint sun line. A faint mark that wanders is just a crease. Neither is a problem.
If you have a pile of little lines there
This is probably the most common case, so it gets its own section. Many hands have not one clear line under the ring finger but several short ones, like a crosshatch. That is not a sun line, and the old authors had something to say about it.
Edward Heron-Allen's 1885 manual is blunt:
"Many little lines upon the mount point generally to an excess of artistic instinct"
He goes on, a few lines later:
"With two or three lines, a subject will often follow two or three different branches of art, without succeeding particularly in any one."
If you have ever started a drawing course, a guitar and a pottery wheel in the same year, that sentence may feel familiar. A hand with many interests gets called scattered, and a hand with one clear line gets called gifted, and I would not take either label to the bank.
Why most hands do not have one
Here is the part the "success and fame" pages skip. Benham ran through how often each main line goes missing, and the sun line comes near the bottom of the list:
"The line of Saturn is frequently absent, and the lines of Apollo and Mercury more frequently so."
In his chapter on the Apollo line itself he is plainer: by far the greatest number of hands he examined had no Apollo line at all. And he did not think the missing line meant anything bad:
"It is absolutely incorrect to say that the absence of a line of Apollo indicates ill success in life"
That is a palmist, in 1900, telling other palmists to stop saying it. So why did they? He explains that too:
"Palmists who have a pleasant story to tell, get the most clients, and this being known to professionals, leads to a system of flattery totally out of proportion to the subject."
A good sun line is a flattering thing to find, so readers found it on hands where it was not. Benham also said that of the people who do have a good one, most lean on their talent and skip the hard work, so less gifted plodders often get further.
Why the old books loved it
Cheiro, a famous palmist and one of the library's most quoted authors, gave the sun line more weight than almost any other author. He called it "one of the most important marks on the hand to consider", and he made big claims for it:
"Without this line the life has no happiness, no sunshine, as it were, and even the greatest talents lie in darkness and do not produce their fruit."
That is a harsh sentence, given that most palms lack the line. Heron-Allen says much the same in drier words: no line means a want of success in the projects that would have led to glory. For people who do have one, Cheiro softened:
"People with the Sun Line appear to have more magnetism, more influence over others."
He also said it works as a booster for the other lines:
"with a well-marked Sun Line even a poor Line of Head promises more success, and it is the same with the Line of Fate."
You can read more on the head line if you want to see how he handled that one. Others were cooler. Phanos kept his verdict to a single modest line:
"It gives success through one's own ability."
The island tease, and the author who laughed
The older books did not stop at talent. They tied marks on the sun line to money and reputation: stars for good fortune, forks for money from two sources, an island for trouble. Leo Markun, writing in 1925, repeated the list and was visibly unimpressed:
"An island on the Line of Apollo is supposed to show the loss of a position, because of the plotting of enemies."
On the star, which the books called a very fortunate sign, he wrote:
"It may simply be success in getting through life without ever being sent to jail."
The books did the same thing to the marriage line, reading dates and counts into it. Small marks on a small crease are easy to over-read, and Markun knew it.
A weak or missing sun line
This is where the books split in two, and I think it is the most useful part of the subject. Cheiro and Heron-Allen read the absence as a lack. Benham, fifteen years after Heron-Allen, called that wrong. Both camps were looking at the same hands. Since most hands lack the line, Cheiro's "no sunshine" would cover most of the people he ever read for, and it does not even hold up inside the old books.
If you came here because you looked at your palm and found nothing under the ring finger, the most careful author in the library says that is the ordinary case.
Questions people ask
Is the sun line the same as the Apollo line?
Yes. Apollo line, sun line, line of success, line of brilliancy and art line all name the same vertical line. Apollo is the Greek sun god, and Cheiro used the first three names in one sentence.
Is it bad if I do not have a sun line?
No. Benham called that reading absolutely incorrect, though Cheiro and Heron-Allen disagreed.
Where exactly does the sun line start?
The authors disagree. Farwell says the Mount of the Moon or the center of the hand, and Cheiro lists several starting points.
Does a sun line mean fame?
No. Some old books said so, and Benham warned that palmists flattered clients with exactly that.
Which hand should I look at for a sun line?
Both. Phanos called the left the hand you are born with and the right the hand you make, so a line that shows on only one is a faint one at best.
Read your own hand
If you want to see whether you have a sun line, and what the old authors said about the rest of your palm, you can read your own hand with Alma. It is free, with no sign-up. You take a photo of your palm, and Alma points out the lines she can see and quotes the books that mention them, including where they disagree.