A poem, hidden in Santa's portrait

At the back of the Entry Hall is a portrait of Santa:

Looking closely we can see it in more detail:

And zooming in, there are some letters hidden in the portrait:

Some of them are a bit tricky to find, but if you're patient enough, you will find the phrase NOW I SHALL BE OUT OF SIGHT, a line from a poem by Hannah Flagg Gould titled Jack Frost:

The Frost looked forth one still, clear night,
And whispered, “Now I shall be out of sight;
So, through the valley, and over the height,
In silence I'll take my way.
I will not go on like that blustering train,
The wind and the snow, the hail and the rain,
That make such a bustle and noise in vain,
But I'll be as busy as they!”

So he flew to the mountain, and powdered its crest;
He lit on the trees, and their boughs he drest
With diamonds and pearls; and over the breast
Of the quivering lake he spread
A coat of mail, that it need not fear
The downward point of many a spear
That he hung on its margin, far and near,
Where a rock could rear its head.

He went to the windows of those who slept,
And over each pane, like a fairy, crept;
Wherever he breathed, wherever he stepped,
By the light of the morn were seen
Most beautiful things; there were flowers and trees;
There were bevies of birds and swarms of bees;
There were cities with temples and towers; and these
All pictured in silvery sheen!

But he did one thing that was hardly fair-
He peeped in the cupboard, and finding there
That all had forgotten for him to prepare-
“Now, just to set them a-thinking,

I'll bite this basket of fruit,” said he,
“This costly pitcher I'll burst in three;
And the glass of water they've left for me
Shall 'tchick' to tell them I'm drinking!”