Royal Baking Powder Co., New York.

This Department is conducted in the Interest of Bicyclers, and the Editor will be pleased to answer any question on the subject. Our maps and tours contain many valuable data kindly supplied from the official maps and road-books of the League of American Wheelmen. Recognizing the value of the work being done by the L.A.W., the Editor will be pleased to furnish subscribers with membership blanks and information so far as possible.

This week we begin describing the trip from Chicago to Waukesha. A trip in the vicinity of Waukesha was given last week as being one of the best rides in that part of the country. The quickest way, of course, to reach Waukesha is by train, but it is a pleasant ride all the way from Chicago there on the wheel, and there is no reason why a wheelman with some time on his hands should not begin his journey at Chicago instead of at Waukesha. There are several ways of reaching Waukesha, but the one that we shall give in the next three weeks is usually considered the best, since it goes through the most attractive country, and over, on the whole, the best roads, although the distance is somewhat greater than by one or two other routes.

The first stage will be from the Court-House in Chicago to Wheeling, a distance of about twenty-five miles. Leave the Court-House, and run out Washington Boulevard, through Union Park to Hoyne Avenue; then turning to the right into this, run to North Avenue, and turn here sharp to the right, and a moment later to the left into Milwaukee Avenue. Milwaukee Avenue runs out beyond Grayland, turns here slightly to the northward, and crosses the railroad track. It is what used to be called the old toll road, and crosses the railroad track at Jefferson Park. Immediately after crossing turn to the left, and follow the track up through Norwood Park, which is two miles further on, thence through Canfield to Park Ridge, and at Park Ridge leave the railroad track and turn right into the road that runs northward. This should be followed as marked on the map, with a sharp turn to the left and right about a mile out of Park Ridge, and a mile further on another sharp turn to the right, bringing the rider again into Milwaukee Avenue. Here keep to the left, and run northwestward through Grove to West Northfield, seven miles from Park Ridge. Thence the road zigzags three or four miles on to Wheeling.

The road most of the way is reasonably good, partly block pavement, and partly ordinary country road in good condition. The run can easily be made in two hours by a moderately good rider; in three hours by any one who is able to ride twenty-five miles. If the rider has time it is well worth while to do this ride in the morning, and spend the afternoon at Wheeling, or running out here and there in the vicinity of that town—to Deerfield, for example, and back. Or it is quite possible to make the next stage of the journey to Waukesha in the afternoon, and this will be given in the coming week.

Note.—Map of New York city asphalted streets in No. 809. Map of routes from New York to Tarrytown in No. 810. New York to Stamford, Connecticut, in No. 811. New York to Staten Island in No. 812. New Jersey from Hoboken to Pine Brook in No. 813. Brooklyn in No. 814. Brooklyn to Babylon in No. 815. Brooklyn to Northport in No. 816. Tarrytown to Poughkeepsie in No. 817. Poughkeepsie to Hudson in No. 818. Hudson to Albany in No. 819. Tottenville to Trenton in No. 820. Trenton to Philadelphia in No. 821. Philadelphia in No. 822. Philadelphia-Wissahickon Route in No. 823. Philadelphia to West Chester in No. 824. Philadelphia to Atlantic City—First Stage in No. 825; Second Stage in No. 826. Philadelphia to Vineland—First Stage in No. 827; Second Stage in No. 828. New York to Boston—Second Stage in No. 829; Third Stage in No. 830; Fourth Stage in No. 831; Fifth Stage in No 832; Sixth Stage in No. 833. Boston to Concord in No. 834. Boston in No. 835. Boston to Gloucester in No. 836. Boston to Newburyport in No. 837. Boston to New Bedford in No. 838. Boston to South Framingham in No. 839. Boston to Nahant in No. 840. Boston to Lowell in No. 841. Boston to Nantasket Beach in No 842. Boston Circuit Ride in No. 843. Philadelphia to Washington—First Stage in No. 844; Second Stage in No. 845; Third Stage in No. 846; Fourth Stage in No. 847; Fifth Stage in No. 848. City of Washington in No. 849. City of Albany in No. 854; Albany to Fonda in No. 855; Fonda to Utica in No. 856: Utica to Syracuse in No. 857; Syracuse to Lyons in No. 858; Lyons to Rochester in No. 859; Rochester to Batavia in No. 860; Batavia to Buffalo in No. 861; Poughkeepsie to Newtown in No. 864; Newtown to Hartford in No. 865; New Haven to Hartford in No. 866; Hartford to Springfield in No. 867; Hartford to Canaan in No. 868; Canaan to Pittsfield in No 869; Hudson to Pittsfield in No. 870. City of Chicago in No. 874.

Any questions in regard to photograph matters will be willingly answered by the Editor of this column, and we should be glad to hear from any of our club who can make helpful suggestions.

MYSTERY OF SILVER PRINTING—(Continued).

Chemists have proved that no substance is sensitive to light when perfectly pure and kept by itself in a dry place. If silver chloride is placed in a glass tube, the air exhausted, and the tube hermetically sealed, it may be exposed to sunlight, and will remain unchanged in color.

The action of light on the silver chloride is to separate the chlorine from the silver, but there must be some substance with which the chlorine will combine, or the light will not decompose the chloride. (Decompose is to separate the parts composing a compound body.)

For purposes of photography some substance must be used which will combine very quickly with the silver, and such a substance is found in silver nitrate. The chlorine set free by the action of light combines at once with the pure silver in the nitrate of silver. The chemical nature of the dark-colored substance produced by the action of light on the silver chloride is not yet fully determined, but most chemists agree that the silver chloride, when decomposed by light, produces silver sub-chloride and chlorine. (A sub-chloride is a chloride which contains more of the base than the acid. A molecule of silver chloride contains one atom of silver and one of chlorine, while a molecule of sub-chloride contains two atoms of silver and one atom of chlorine.)

This silver chloride is white, but passes through different shades of coloring, from a reddish-violet to a deep purplish-black, according to the length of time it is exposed to the light.

When paper coated with a sensitive silver solution is placed under a negative and exposed to the sun, the light reaches the paper through different degrees of thickness, or density, in the gelatine film. In the part of the negative which represents the sky the film is quite thick, while in the part which represents the deep shadows it is thin, sometimes being almost transparent. The part of the paper which is under the portion of the negative representing the sky is scarcely affected by the light, but in that part representing the shadows the light acts at once, and quickly decomposes the silver chloride. When the paper is taken from the printing-frame it contains different grades of the deposit formed by the action of light on the silver chloride.

Note.—The first article in the series of "Chemistry of Photography" was published in No. 867 (June 9). This article was on the chemical elements, and contained the following paragraph:

"Each element is represented by a symbol, this symbol being the first letter or letters of the name of the element. The symbol of hydrogen is 'H': of oxygen is 'O'; of gold, 'Au,' the first two letters of the word 'Aurum,' the Latin name for gold. Each symbol also stands for the weight of one of its atoms. (An atom is supposed to be the smallest possible division of a substance.) Hydrogen is the lightest element known, and is taken as the standard of weight when comparing the weight of other atoms. The symbol 'H' would therefore not only stand for the element hydrogen, but for its atomic weight, 1, or a unit. An atom of oxygen is sixteen times as heavy as an atom of hydrogen, and an atom of gold is 196 times as heavy."

In the next number of the Round Table a list of the chemicals mentioned was given, but either through a typographical error or an error in copy, the weight of hydrogen was given as "11," and that of oxygen as "12." It should have been hydrogen "1," and oxygen "16." Those who read the first paper would of course perceive the mistake; but this correction is made for those who may not have seen the first article, or may have forgotten the explanation.

[CAPTAIN JACK AND THE CANNIBALS.]

"Well! well! well!" said old Captain Jack, as Bobbie and Tom appeared before him on the beach in front of the Ocean House. "You boys back again, eh? Why, do you know, I never expected to see ye again? For a fact I didn't."

"Why not?" asked Bobbie.

"Why not?" echoed the old seafarer, as he leaned back against the old wreck and laughed. "Why not? Why, I takes the town paper, I does, an' las' winter I seed a squib in the town paper as said that two hungry cannabiles had descended on New York city, an' et up the whole poppylation. Mebbe you didn't belong to the poppylation. Some folks don't join everything there is a-goin'. Wasn't ye et up?"

"How you do talk!" said Bobbie. "If we had been eaten up how should we be here?"

"Simple enough! simple enough!" returned the old Captain, pulling away on his pipe. "I was et up once, therefore why not ye, says I," he added.

"Eaten up? You?" cried Tom. "How could that be? You are here, aren't you?"

"Yes, I be," returned the Captain. "But so also are you in spite of the fact that ar town paper says that two cannabiles has et up the poppylation of New York. If it's a-comin' to manufacture apologizing, it's your turn first."

"Well," said Tom, "we don't want to make you mad, Captain Jack. If two cannibals ate up the population of New York, we escaped. Maybe we were in the back of the pantry, where they couldn't find us," he added, with a sly wink at Bobbie.

"That's where I was," said Bobbie, resolved to be on good terms with the Captain anyhow. "I heard our next-door neighbors hollering away like everything, so I and my whole family hid away behind the ice-box."

"Exactly," said Captain Jack, with a smile. "You was sensible, you was; an' so you escaped being et, but I never had no such luck. Cannabiles got hold of me oncet, an' if it hadn't been for my presence o' mind I wouldn't ha' been here now."

"Why, what did they do?" asked Tom.

"They et every bit o' me except my head," said Jack. "First they et my feet, then my legs, then my arms, an' then the rest o' me, except my head"—and Captain Jack sighed as he thought of it. "An' I tell ye, boys," he added, with a sad shake of his head, "it hurt awful, 'specially when they were pickin' my bones."

"But you're here now!" cried Bob.

"Yes," said Captain Jack; "but from my collar down I'm false. I've one wooden leg, one cork leg—which keeps me up when I go in swimmin'—one wax arm, and another arm which I've growed since the cataract."

"Cataract?" said Bob.

"Cat-as-trophe, I guess you mean," said Tom.

"One o' the two. I dun'no' which," said the old sailor. "I ain't never been particular about cats."

And then he rose up and walked away, leaving the two boys wishing they had brought a few pins along with them to stick into him to see whether his legs were really cork and wood, as he had said.