We consider this the most effective invention that has yet been offered to the gardener for marking his plant-labels. The writing is black and indelible, the labels requiring no other preparation than previously rubbing them with a damp finger. The label may be either of wood, parchment, bone, or zinc. The pencil requires no cutting, but the writing-points are raised or lowered in a mode similar to those in Mordan's lead-pencil cases. It is equally efficacious for marking linen, and when our readers remember the trouble and difficulty of obtaining clean and efficient quill pens for applying marking-ink, we think that they will not be slow in patronizing "Dunn's Solid Marking-Ink Pencil." The case and point are only eighteen pence.

We have no doubt Mr. Dunn will advertise this very clever and useful invention, and in the meantime we publish the following letter we have received from him:

"At last I have the pleasure to forward you one of my Solid Marking-Ink Pencils, which after eighteen months' hard work have been brought to their present form. The Cedar cases in which I at first tried them proved a sad mistake; the oil contained in the wood softened the points and caused the pencil to block up, and this I did not discover until I came to make them in bulk. It is a curious fact, that in the Cedar cases the oil will not act on them if carried in the pocket; whereas, if the same point is put in a Cedar case and left in a cool place, the oil condenses on the point and softens it in the course of two or three days.

"The white wood case contains no oil, and some I have had filled in for three months are as good as ever. I tried an old point the other day, one of the first I made fourteen months ago, and found it much improved by age. This was very satisfactory, as some of my chemical friends predicted a decomposition of the points; but facts prove the contrary.

" No preparation is required for marking sticks, etc.; the slightest damping is sufficient, and they will mark dry; and if you want to fix the writing at once, hold the stick to the fire just below scorching heat.

" It will also mark permanently on linen, etc, dry, or slightly damped with water or the tongue, but not so black as with the tartrate of potash. I could put them up in white wood as a common pencil, but there is a great objection to cutting them - they mark the thumb, and the cuttings mark anything they fall on. I have also tried to cheapen them, by using a common slide, but they do not work so well as with the screw, and as this is a patent case, I am obliged to pay a high price for it; but you will understand they refill for la. I send you a specimen written on calico, which has been washed several times." - Cottage Gardener.