tions usually employed,—a matter of interest when we consider the phosphate of lime required for certain plants,—we should recollect that when free carbonic acid is present in water, the phosphate, like carbonate of lime, though not to the same amount, is very soluble. Hence, especially when, as noticed by Mr Austen, phosphate of lime is disseminated in the state of fresh corprolites amid detrital matter, and water containing free carbonic acid is present and can have access to it, the phosphate of lime would be in a condition to be removed and disseminated. Mr Austen has alluded to the mixture of such bodies with vegetable matter, to the decomposition of which, with animal matter also, we might look for some, at least, of the carbonic acid that would aid the solution of the phosphate of lime. As in the case of the carbonate of lime previously noticed, when the solution of this phosphate met with the silicates of potash or soda, whilst percolating amid the rocks, the silicates would be decomposed by the carbonic acid, and the phosphate of lime thrown down. We should expect, in the same manner as carbonate of lime often replaces the original matter of a shell which has been decomposed and removed from the body of a rock, leaving those cavities commonly termed casts,--that phosphate of lime, in localities where, from accidental circumstances, it was somewhat abundantly filtering through rocks, would also enter these and any other cavities, filling them under the needful conditions of deposit. In like manner as we find carbonate of lime separating itself from mud and silt in which it was disseminated, forming the nodules so common in calcareo-argillaceous deposits, should we also expect disseminated phosphates of lime to do the same under fitting conditions; so that it would not necessarily follow, however true in numerous cases, that nodules containing much phosphate of lime were coprolitic. We can readily imagine circumstances very favourable for the solution and spread of these phosphates amid layers of mud and silt. We find such phosphates surrounding some fossils, such as crustaceans from the London clay, leading us to infer a connection between the animal matter and this substance.

On a New Species of Manna from New South Wales. By THOMAS ANDERSON, M.D., F.R.S.E., Lecturer on Chemistry, and Chemist to the Highland and Agricultural Society of Scotland. Communicated by the Author.

The saccharine exudations of plants which have been classed under the generic term of Mannas, present, in all instances, a close resemblance in their chemical constitution. Their

principal constituents are, gum, sugar, and the peculiar principle called mannite, which derives its name from its source, and has been considered as the characteristic constituent of a manna. All the varieties of manna obtained from European or Asiatic plants which have been examined contain this substance in greater or less abundance, and it appears also to be a common constituent of the fluid exudation of the leaves known by the name of Honey-dew. At least, this is certainly the case under certain circumstances, as it was observed by Langlois in the honey-dew of the lime, which, during the hot summer of 1842, occurred in such abundance in the neighbourhood of Strasburg, that it fell from the trees in the form. of small rain.

About 30 years since, a species of manna was brought to this country from New South Wales, which was obtained from the Eucalyptus mannifera, and differed in many of its properties from the European mannas. This substance was examined by Dr Thomas Thomsont, who ascertained it to contain a species of sugar resembling, and yet different from, mannite. It was afterwards examined by Professor Johnston‡ who confirmed Dr Thomson's observation, and by analysis obtained for this new species of sugar the formula C12 H14 0142 which removes it altogether from mannite, and brings it into the class of the true sugars, containing hydrogen and oxygen. in the proportion to form water, and further establishes its isomerism with grape-sugar, from which, however, it manifestly differs in all its properties. This was the first manna examined which contained no mannite; and I have now to add to the list another, similar in this respect, but differing in every other, and peculiarly remarkable from its possessing a regularly-organised structure.

The specimen subjected to analysis, I owe to the kindness of Mr Sheriff Cay, by whose son, Mr Robert Cay, the substance was originally discovered in the interior of Australia Felix, to the north and northwest of Melbourne. An immense

* Journal für Practische Chimie, vol. xxix., p. 444. † Organic Chemistry, Vegetables, p 642.

Journal für Practische Chimie, vol. xxix., p. 485.

tract of country in this district is entirely occupied by a "scrub," as it is called in Colonial language, consisting of the mallee plant, Eucalyptus dumosa, the leaves of which at certain seasons become covered with this species of manna, which is known to the natives by the name of Lerp, the 7 being pronounced like the Italian gl. This substance was first observed by Mr Cay in the latter part of the year 1844, when he explored a considerable district lying between lat. 36° 20′, and 37° 10′ S., and long. 142° 40′, and 144° 20′ E. in search of pasturage for sheep. He returned in 1845 to occupy the ground, and, in the course of his journey was obliged to leave his party, in pursuit of a native guide who had decamped with a gun. In mentioning this incident, Mr Cay writes (25th March 1845): "I was rather cold that night, as I had come off after him in my shirt-sleeves; moreover, I had no dinner, but I got plenty of lerp. Lerp is very sweet, and is formed by an insect on the leaves of gum-trees; in size and appearance like a flake of snow, it feels like matted wool, and tastes like the ice on a wedding-cake."

On Mr Cay's arrival in Scotland in 1847, he gave some further particulars regarding this substance, stating that it was produced in great abundance, and covered large tracts of the scrub like snow; that it is very nutritive, the natives becoming fat during the season in which it is found, and that he himself had subsisted for a day or two upon it; that it adheres with very little tenacity to the leaves, and is immediately washed off by a shower of rain.

As it appeared from this description, that the substance was unknown in this country, Mr Cay, at his father's request, wrote to his overseer in Australia, who sent over the quantity of lerp which has formed the material for my observations, accompanied by a letter, dated 25th February 1848, of which the following is an extract:-" The Blacks say the lerp is not in any way produced by an insect, but that it is a spontaneous production of the mallee or gumscrub when very young, say a foot or eighteen inches high, and that it grows on either side of the leaf; that old mallee or mallee about eighteen inches high, does not produce lerp.

Therefore, this year they have burned as much of the mallee as they could to admit of the young mallee springing up."

The only published notice of this substance I have met with, is contained in Westgarth's Australia Felix, page 73, where it is mentioned in the following terms :-" Mr Robinson, the chief protector (of the Aborigines), ascertained during his expedition, in 1845, to the north-west of Australia Felix, that the natives of the Wimmera prepare a luscious drink from the Laap, a sweet exudation from the mallee (Eucalyptus dumosa.) This liquor is manufactured in the months of February and March, on which occasions there is commonly a festival and adjustment of mutual disputes."

The substance to which these observations refer, differs very strikingly in its external appearance, from all the other species of manna. It consists of numerous small conical cups of the average diameter of one-sixth of an inch, with a more or less distinctly striated structure, and covered externally with a number of white hairs curled in various directions. These hairs are not distributed over the whole external surface of the cup, but are generally attached to the middle portion between its base and apex. The cup itself is generally sharply acuminated, and bears a pretty close resemblance to some of the smaller species of patella. Its interior is pretty smooth, its exterior rough, and its edge perfectly regular and round. The cup and hairs are translucent, except on the edge of the former, which is frequently opaque. No traces of attachment to the leaves of the plant were to be detected, and though fragments of leaves, obviously those of a species of Eucalyptus, were found in the substance, none of them had any of the cups attached to them. The cups were not generally isolated, but usually adhered loosely to one another by the edges, and this attachment was always such that the mouths of the cups were in one plane, and there can be little doubt that it was by this surface they were attached to the leaves. The bairs, when examined under the microscope, were found to be distinctly organized. Each hair formed a uniform tube, which, under a high magnifying power, presented a granular structure,

with imperfect indications of transverse striæ. When treated with potash under the microscope, they became very transparent, and lost their granular appearance, and a drop of solution of iodine coloured them uniformly blue; thus indicating starch as one of their constituents. The cup itself is composed entirely of a mass of cells resembling starch-globules, but so closely compacted together, that their characters can only with difficulty be made out. A thin slice, however, when macerated for some time in water, admitted of disintegration, and though most of the cells were broken up, a few could be distinguished in a pretty perfect state, and agreed in their appearance with those of starch. The whole cup is coloured blue by iodine.

The taste of lerp is distinctly saccharine, but this is confined entirely to the hairs; the cup when completely separated presenting only a slight mucilaginous taste.

The chemical examination shewed that it differed as remarkably in constitution as it does in form, from all hitherto examined species of manna. When boiled with alcohol, a large proportion is dissolved; but the solution deposits no mannite on standing, and when evaporated on the waterbath, yields a thick syrup, which cannot be brought to crystallise. It is obvious, from this fact, that it contains neither mannite nor the sugar obtained by Johnston from the manna of Eucalyptus mannifera. The sugar separated from lerp had all the characters of the uncrystallisable sugar obtained from fruits, and entered rapidly into fermentation when mixed with yeast. The residue from which the sugar had been extracted yielded to cold water a small portion of gummy matter, and, when boiled with water, a considerable part of it dissolved, and the filtered solution, on cooling, deposited a large quantity of a white powder, of sparing solubility in cold water. The fluid from which this substance had separated gave, with iodine, a strong reaction of starch.

The substance which deposited from the hot solution, when washed with hot water until it no longer gave the reaction of starch, was found to agree, in all its characters, with