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any information; but our watchword was "onward," | It appears to be approved both in France and

and the day was one of the hottest of the three or four hot days which the Exhibition has yet experienced.

Before leaving the subject of this Exhibition, I must once more advert to microscopic matters connected therewith; not that I have any reason to alter the general opinion expressed in "A Voice from Paris," but to add one or two facts then unnoticed. First of all comes the discovery in the French department of a microscope with a moveable stage and a lever, and still more surprising a large microscope (not quite so large as No. 2 size of the London opticians), with two rack-work movements to the stage. I must add that the exhibitors of these phenomena are Mirand & Fils, Rue Galande, 52. It is but fair to add that the Parisian opticians are not at fault in shunning stage movements and other improvements, but, as a friend writes me from another corner of the Continent, there is a reason at the bottom. "I read with interest," he says, "your remarks on the microscopes. You are certainly quite right in reflecting on the small dimensions of the continental instruments, and on the very general non-adoption of machine stages and inclining joints, but you might have given (if you could have done so without offence) the true reason-a desire for cheapness. A German or Frenchman likes the luxury of a Ross, Smith and Beck, or Powell and Lealand, as much as any one, and when they affect to despise English appliances on principle, I never believe them."

I have also seen the working of high powers constructed on the "immersion" principle, at a comparatively cheap rate, and certainly with excellent results. I am disposed to think that we know too little of these objectives in England, and have hitherto regarded them with a trifle too much of prejudice. Fancy, for instance, looking at Pleurosigma angulatum, with an apparent diameter of about two inches, without artificial light, or condenser of any kind, and, more than all, mounted in the ordinary manner, with the common thin glass, not extra thin glass, and being able to take the slide off the stage without moving the objective out of focus. The magnifying power is said to be equal to about th of an English inch, and the price 300 francs. Messrs. Hartnack exhibit objectives of a very superior character to those heretofore manufactured in France; and their new pattern objectives, without immersion, are spoken of by all who have tried them in terms of high praise. On this point, however, I am only echoing the opinions of others, although my own impression, from a casual peep or two through one of them, is much in their favour.

By the way, I am not aware that the spot lens, with the spot on the plane face of an inverted cone of glass, described by M. Nachet, in the Microscopical Journal some years ago, has been used in England.

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HOME is not shut within narrow limits, is not

confined to scenes of pleasure, regal splendour, or the dwellings of the great. Wherever warm hearts are to be found together, with contentment and a hearty desire at all times to do the best that can be done under existing circumstances, health and strength, a will to work, and an unwavering trust in God, who cares even for the sparrows,-there, believe me, exists the primal elements, the magic of home. Thus writes Mr. J. K. Lord at the commencement of a book* which he has just issued with the above title, and which is intended to teach all wanderers how, if they have but the will, they may make themselves "at home in the wilderness." One of the most important requirements for such a task the author possesses, a long experience on the subject of which he writes. Still another scarcely less welcome recommendation will be found in the interesting, aye, fascinating manner in which he inveigles his reader into following him through what a less efficient hand would have left a dry detail of makeshifts about as interesting as a cookery book or a pharmacopoeia. The object of the book is equally achieved, but in a different manner. We learn "where and when to camp; how to equip and manage a train of packmules; break, gear, and saddle wild horses; cross streams, build log shanties, trenail a raft, dig out a canoe, or build it with bark or hide; manage dog sleighs, and tramp on snow shoes; what to carry, and what to leave at home;" in fact, all that a wanderer would desire to know, freely interspersed with illustration and anecdote, joined with hearty and wholesome advice, and all so disguised that we fancy we are reading a new book of travels which we cannot leave until it is finished, and which has the merit all books of travel do not possess, of leaving the reader a wiser man.

Let us collect an incident or two from this little volume in illustration of our remarks. No one would think it a matter of much consequence in buying a horse whether the animal had a long tail or a short one. Oh, yes it is! says Mr. Lord. "In

"At Home in the Wilderness: being full instructions how to get along, and to surmount all difficulties by the way." By "The Wanderer." 323 pp., post svo. London: Robert Hardwicke.

proof of the value of a horse's tail, in a country infested with blood-sucking flies, I may state that I once, when at Walla-Walla, a small steamer-landing and town situated at the head of navigation on the Columbia river, purchased a Siskyoo horse, which means a horse with its ears cropped short like a terrier's, and a tail cut off close up to the rump. This is, or once was, a common custom with the Siskyoo Indians, and all horses so trimmed are designated by the generic name of "Siskyoo." The object of this barbarous custom was to enable these Indians easily to recognise their own horses if stolen and subsequently discovered herding with other bands. Horse-stealing is the primary cause of nearly every Indian war and quarrel. The poor Siskyoo beast, although as perfect a cob as any man need have looked on, was nevertheless utterly valueless during the summer; unable to whip away his tormentors, they worried him with impunity, until want of rest and continuous irritation reduced him wellnigh to a skeleton. When found make a note of.' Always look out for long-tailed mules and horses in a fly country."

The author of this book was Naturalist to the British North American Boundary Commission, and when reading his account of one difficulty which he had to surmount to the west of the Cascade mountains, we could not help wondering what some of

Fig. 90.

our "parlour naturalists" would have done in such a strait. The place is now called the Diamond Tree Pass. "It certainly was an awful place up which to make a trail that should be available for packed mules, and, to add to the difficulty, a goodsized stream of water tumbled rather than ran down the hill-side. The distance from the base to the summit, in a straight line, was not more than three-quarters of a mile, but it was rocky and densely timbered. The difficulty, too, was the more

complicated, inasmuch as the prairie leading to the pass was intersected by several streams not fordable, and two swamps that must be crossed. I thought the matter carefully over, climbed up and down the hill, and recalling the words of Napoleon, 'Impossible, c'est le mot d'un fou,' finally made up my mind to do it. By describing how this apparent impossibility was overcome, I shall give all the practical hints relating to trail-making, bridge-building, and fording swamps which a wanderer can require." But our space will by no means permit us to narrate how it was done, and we can only recommend all who desire to know, to procure the book and read it for themselves.

In compensation for omitting the details of the Diamond Tree Pass, we purpose to conclude with the picture of a "buffalo run" :

"The scene of my adventure is on the broad plains in the Red River settlement. The sun is just creeping from behind the eastern hills, tinting with the rosy hues of morning the splintered summits of many a far-off peak, and at the same time shedding a paler glow over the grassy slopes; the different intensities of the light give to the flat surface of the plains the appearance of being an ocean of mist. A band of Red Indians with whom I am hunting and living are mounted and ready for the hunt, and few have ever looked upon a more picturesque

sight. Their only garment, a piece of skin tied round the waist, makes the muscular figures of the savages look more like exquisite carvings than real flesh and blood. Thus sitting their prancing half-tamed horses with matchless ease and grace, their black hair flowing in tangled locks down their backs, confined only by a narrow band of ermine-skin, with an eagle's feather sewn to it, they look as wild and fearless as the beasts they are about to chase. We are waiting for the mist to rise, which it will do when the sun comes fairly above the horizon. Ah! there it goes, the fog lifting like a veil. It does not evaporate, so to speak, and disperse, but rises en masse like a balloon, and at once becomes invisible. And now we can make out the buffalos scattered over the plain. Some are busily cropping their dewy breakfast, others are still lying down in little groups-but all are in happy ignorance of the dire enemies lurking behind the knoll watching their every movement. Craftily, and with extreme caution, we walk our horses to windward of the herd, and as we emerge from the cover of the ridge, the trumpet-like notes of the older bulls tell us that we are discovered. Concealment is now of no further use, the

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beasts are crowding together like sheep when scared by a dog. The Indians give a piercing whoop, and we dash wildly after the now rapidly retreating herd, their tails upheaved and their horns rattling noisily against one another. The very plain seems to shake, clouds of blinding dust, raised by thousands of hoofs, nearly hides the hunters from each other, whilst a rumbling noise, like subdued thunder, seems to absorb and swallow up all other sounds. I soon overtake the rearmost animals, and singling out a young cow, drop her in her tracks; recharge my gun, and single out this time a fine old bull. He seems to roll rather than gallop along, his nose nearly touching the grass, and his shaggy brown mane tossing wildly in the breeze. My horse, though thoroughly up to his work, appears to know by past experiences that it is no mean foe he has to deal with; laying back his ears, and pushing out his nose, as if to make the most of every breath of air, the gallant mustang thunders on at such a pace that I find myself side by side with the shaggy bull before I have time to think of my position in reference to the other stragglers of the herd. or lose my chance. trigger.

Now or never I must fire, Lowering my gun, I pull the

It appeared to me that the cap had hardly exploded ere my mustang wheeled short about with such startling velocity, that it was with the utmost difficulty I contrived to retain my seat; but as if the fates were against me, two other buffalos were directly in the way, and for a few seconds prevented the horse from galloping away from the bull, which, turning nearly as rapidly as the horse, charged, and striking the horse on the point of the shoulder sent us both rolling on the plain. I was terribly frightened and shaken, but adopting Falstaff's maxim, ‘that the better part of valour is discretion,' I lay still to await the issue of events. The mustang had by this time regained his legs, and was, with evident difficulty, limping away as fast as his damaged shoulder permitted. That the bull was badly wounded I could see by his rolling gait, heavy breathing, and the bloody froth besmearing his nostrils and lips. I do not think he saw me, for his glaring eyes were directed towards the horse, which he made a vigorous attempt to follow; but it proved a signal failure. The wounded beast seemed to be perfectly aware that if once he fell to the ground all hope for him was at an end, so bracing his muscles firmly, and planting his massive legs wide apart, the powerful animal seemed determined to stand up to the last. Hurt and frightened as I was, I felt sorry for him; the eyes lost all their fire, and a saddened expression took its place. He tried to get glimpses of his comrades, by this time nearly lost in the distance; and I know that dying buffalo was quite aware that he should never see them again. His great chest was heaving convulsively,

and low plaintive sounds, more resembling sobs than anything else I know of, told in language plain as printed words how terrible were his sufferings. The head dropped, until the nose was nearly touching the grass, the ponderous body rocked like a storm-tossed ship from side to side, a gurgling sound replaced the stentorous breathing; then suddenly the muscles seemed to lose all further power, and with a heavy crash the king of the plain fell dead amidst the grass and wild flowers. The Indians soon recovered my lost steed, for his shoulder was so much injured that he could only contrive to limp slowly away."

Of course every wanderer in the future will read this book before he starts on his travels, and so should every one who stays at home, unless his home is a wilderness, and he desires to make it a desert.

UNDE

SOCIABLE MITES.

NDER the name of "Sociable Mites," I am desirous of interesting those who have opportunities for observing the small organisms which make their appearance during the summer months, on behalf of a little known group of Acari, which are associated by naturalists under the generic name of Tetranychus. Scattered notices occur of the appearance of some of these minute visitors in immense numbers in former years, and now, being forewarned, it is hoped that some of the readers of this journal will be prepared to add a little to our knowledge should they encounter any of the little creatures about to be alluded to, during their summer rambles.

There are probably about twenty different species of this genus described, and a few only of them have as yet been certainly known to inhabit the British Isles. Several have the singular habit of living in very large communities, and the history of one species, as described by Dr. Milner Barry in a letter read before the Entomological Society of London in 1855, will serve as an introduction to the rest.

"When strolling across Rusthall Common this afternoon, I noticed some red powder lying in thick cobwebs entangled in the furze. I took up some of the powder, and found it was living and moving, and consisted of myriads of vivacious red insects, resembling Acari." When the mass reached my hands, it was of the size and shape of a sparrow's egg, the Acari running over it in all directions, and each adding to the bulk by leaving behind him a continuous thread of the finest conceivable silk. I subsequently sent the mass to Mr. Meade, the Arachnologist, who has carefully examined it, and kindly sent me the following information :-"The minute animals inhabiting the curious cocoon you sent me are Acari, belonging to the genus Tetrany

chus of Dufour, the type of which is the little red spider so injurious to plants in hothouses and rooms, the Acarus telarius of Linnæus; most of the species live in societies, on plants, and possess the power of forming webs." Koch says, when speaking of an allied species, Tetranychus socius, "It appears in certain years in such numbers that it covers the trunks and the branches of the limetrees which it frequents, with such a thick web that they look as if clothed with glazed satin. I cannot find any description of the species sent by you, although it is closely allied to the common Tetranychus telarius, and I never before saw or found anything like the curious nest which it inhabits." Since the receipt of Mr. Meade's note, I have paid some little attention to the Tetranychus telarius, and find that the network of infinitely minute silken threads is admirably adapted to its singularly formed feet, and these are equally well adapted to the office of holding on while it perforates the cuticle of the leaf with its rostrum; its hold is so secure that no amount of washing by means of a garden engine seems to have the effect of removing it. As I have no doubt whatever that these little creatures are exclusively vegetable feeders, the web cannot serve, as in spiders, the purpose of securing prey, and it is, moreover, never accompanied by the glutinous particles which render the web of spiders so adhesive. As a matter of course, if the Acari can resist the action of a water-engine, they have little to fear from the effects of rain."

which had the trunks and branches entirely or partially covered with a very delicate web, upon which myriads of a small Arachnidous insect were running to and fro, extending their webs rapidly along the branches. The web was so fine as to appear like a thin compact layer of varnish upon the stems of the trees, and from the vast number of the insects, the grey web appeared dusted with a reddish powder, the insects being of a light orange colour, inclining to brown. From the web so completely enveloping the tree and obstructing the vital influence of the atmosphere, the leaves became withered and fell. This was especially the case with the plane-trees, the elms and horse-chestnuts being free from them. The weather for several days previously and subsequently was fine and sultry, but in the course of a few days a heavy fall of rain, accompanied by a thunderstorm, put a stop to the injury by destroying the insects. On placing a portion of the web with its inhabitants in a bottle, Mr. Wilson observed that in about an hour a beautiful transparent cylinder had been spun within the bottle, from the base to the top, impinging against the side of the bottle at about half its height; and it was remarkable that there was not a single thread stretched across the inside of the cylinder, nor was a single insect enclosed within it. Having completed their first cylinder, they threw a second around it, more slender than the former, leaving only a small interval between them.

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The "red spider," as it is called by gardeners, having been alluded to in the above communication, as forming the type of the present genus, it has been figured in this place, although too well known to all who are associated with greenhouses and conservatories (fig. 91) to need further description.

Ten years prior to the above communication by Dr. Milner Barry, the plane-trees in Regent's Park were observed by Mr. George Wilson to be infested by " sociable mites," of which occurrence the following account was transmitted to the society already named :

At the beginning of September, Mr. Wilson's attention was directed to the trees, several of

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Mr. White considered the species to be Trombidium tiliarum, or an allied species, and distinct from Acarus telarius, L., and Trombidium socium, the habits of which, as described by Hermann, were mentioned by Mr. White.

The species described and figured by Hermann and Koch under the name of Tetranychus tiliarius, or the "Lime-tree Mite," is engraved (fig. 92) forthe benefit of my readers. It must be observed that bright colours characterize the majority of the members of this genus, although that feature is omitted in the woodcuts.

Careful readers of the past volumes of SCIENCE

GOSSIP will remember that allusions have been made to a curious little red mite which deposits its white eggs on stones, and similar substances. This

Stone Mite" (fig. 93) is Tetranychus lapidus, and the extract from the Entomologists' Monthly Magazine alluding to it, which was quoted (SCIENCEGOSSIP, 1865, p. 22), need not be repeated here. Gervais states that the eggs may be seen in autumn on the stones of the public promenades in Paris. These eggs (fig. 94) were observed and figured in one of the earliest numbers of Loudon's excellent Magazine of Natural History.

given (fig. 96). It is of a pale colour, and also prefers to consort in colonies.

The "Plum-tree Mite" (Tetranychus prunicolor) is said by Gervais to be found in the months of

Fig. 96. Tetranychus socius.

July and August, on the leaves of the pear and plum trees in some parts of France, and when mature is of a violet-brown colour, but when young, greenish. One species, affecting elm-trees, is called by Koch-Tetranychus ulmi, and is of a bricky red (fig. 97).

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Fig. 95. Tetranychus major.

Another species, which may be called the Laurustinus mite, having a long appendage (Tetranychus caudatus), is found in colonies on the lower surface of the leaves of the Laurustinus, but has not yet been recorded in Britain.

Already allusion has been made to the "Social Mite" (Tetranychus socius), of which a figure is now

Fig. 98. Tetranychus salicis. Fig. 99. Tetranychus Viburni.

The guelder-rose also cherishes its sociable mite, which is called Tetranychus Viburni (fig. 99), and is orange-coloured when mature.

Upon the poplar a greenish mite has been discovered, belonging to the same genus, and which is named by Koch-Tetranychus populi (fig. 100).

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