Godfrey Higgins, The Celtic Druids vol I., ch 1 pt.2

Chapter 1, pt 2

98. I think it very probable that from the use of leaves as letters, the hieroglyphics may have taken their rise. Suppose letters in the shape of the leaves of trees to have been made of thin laminae of gold or tin, and strung on a cord, something like the tripods of the ancient Peruvians, a magical letter would thus be invented which could be deciphered by none but those who understood the secret; and it might be made extremely complicated by the addition of leaves not in the alphabet, or by the forms of other things, between the words or real letters, which would not, to the initiated, increase the difficulty of reading it, but rather the contrary, and at the same time would render it perfectly unintelligible to those not initiated. After some time these leaf letters would be drawn on plain surfaces, and again; with a little more experience, all other kinds of objects would be added to increase the difficulty and mystery, until the leaves would be lost sight of altogether, and the hieroglyphics come to what we find them. [1, p. 17]

This reasoning seems to be nothing but speculation and assertion. He is trying to establish that hieroglyphs were invented later than alphabets, which no serious scholar today would claim or accept.

102. It has been observed by almost every philosopher who has visited the pyramids of Egypt, that they are placed exactly to face the four cardinal points of the compass, from which astronomers know that thier builders must have possessed a very considerable skill in the science of astronomy. This affords a strong presumption that the art of writing must have been known to their builders; they can scarcely be believed to have possessed so much science as the fact seems to require, without it. Now, in the next place, it may be observed that there is not on any one of the larger pyramids the least appearance of of any thing like a hieroglyphic. This fact, combined with the evident knowledge possessed by their builders of astronomy, justifies the presumption that they were built before hieroglyphical writing was known, though perhaps after our mode of writing was discovered. Though the two facts may not be considered to amount to a decisive proof, I maintain that taken together they afford strong presumptive evidence. On the subject of hieroglyphics,
103. Mr. Maurice says, "Before we quit the pyramids, I must be permitted to make one reflection. On no part of the great pyramids, internal or external, does there appear the least sign of those hieroglyphic sculptures which so conspicuously and so totally cover the temples, the obelisks, and colossal statues, of Upper Egypt. This exhibits demonstrative proof, that at the period of the construction of those masses, that kind of hieroglyphic decoration was not invented, for, had that sacerdotal character been then formed, they would undoubtedly not have been destitute of them. [1, p. 18]

Hieroglyphs are found in them, though, so this is pretty decisively debunked. Hieroglyphs are now known to predate the first Egyptian pyramid by a few centuries. We also know Sumerian writing was more hieroglyph-like at about that time than it was alphabet-like, and finally, we roughly do know when abjad writing systems appeared - and this is indeed later than the appearance of hieroglyphic systems.

105. After the celebrated Mr. Belzoni and Lieut.-Col. Fitzclarence had with great labour obtained admission to the inner chamber of the second in size of the pyramids, Mr. Belzoni discovered, from an inscription, that it had been opened before by one of the Califs. It appeared that the contents of the sarcophagus which he discovered had been thrown out, and were lying on the floor at its side. He preserved part of them, which were bones, and brought them to England, never letting them go out of his own possession. These were carefully and publicly examined by several of the first natural philosophers in London, who, to their great surprise, discovered that they were the reamins of an animal of the Beeve kind. Respecting these facts there never has been any dispute. They are perfectly notorious; and neither Mr. Belzoni, nor the natural philosophers, had any theory, interest, or system, to influence their judgments respecting them. Part of the bones may yet be seen, where I have seen them, at the house of Lieut.-Colonel Fitzclarence.
106. I suppose no one will doubt that these bones of an exemplar of the famous God Apis, on which some foolish and absurd priest-ridden king must have been weak enough to lavish such immense labour and treasure. This Bull Apis has been proved by many philosophers to have been the Bull of the Zodiac; in fact, the Sun, when he entered the sign of the Bull in the Zodiac, at the vernal equinox, concerning which I shall shortly make some observations, and of which I shall have much to say in the following work. This being, for the sake of argument, at the present moment admitted, it follows that the Zodiac must have been invented before one of its signs, the Bull, can have become the object of adoration. [1, p. 18]

In case beeve is an unfamiliar word, it basically signifies bovine creatures (an obsolete form of 'beef'). The argument then is that a bull has been, basically, worshipped. This worship can only have been bestowed on it after the Zodiac sign of Taurus had been established, since why would they otherwise adore it? This, to me, seems to be the fallacy of assuming the conclusion. We can just as well claim that veneration of bulls has to have predated the establishment of a constellation as representing a bull in the first place - why else would they place the animal in such a prominent part of the sky?

This post is quote-heavy, but that is basically the best way of showing how uninformed and illogical Higgins was, drawing unjustified conclusions from incomplete evidence.