by exposing to direct sunlight and the ordinary atmospheric influences, patterns of silks, wool, and cotton, specially dyed with the various natural and artificial colouring matters.

The work of purifying these colouring matters, dyeing the patterns, recording the dyed and faded colours of each pattern, &c., &c., must necessarily require much time. Moreover, owing to the very large number of colours to be examined, the long exposure needed to give useful results (one year at least), and the limited capacity of the exposing frame employed, the work will naturally proceed but slowly, and will extend over a period of some years.

During the past year the Secretary of the Committee has been engaged in collecting samples of the colouring matters required for the investigation, and in making preliminary exposure experiments with the view of determining the best method of procedure to be adopted.

Having decided to expose the patterns in groups according to colour, the work of purifying and dyeing with the red colouring matters has been begun, and is now in progress in accordance with a scheme in the hands of members of the Committee.

Of the 201. originally granted to the Committee at the last meeting of the Association in Leeds, the sum of 17. 10s. has been expended in the purchase of the necessary silk, wool, and cotton material, also an exposing frame, which has been erected at Adel in the neighbourhood of Leeds.

Particulars of this expenditure have been forwarded by the Chairman of the Committee to the General Treasurer.

Report (provisional) of a Committee, consisting of Professors M'LEOD and W. RAMSAY, and Mr. W. A. SHENSTONE (Secretary), appointed to investigate the Influence of the Silent Discharge of Electricity on Oxygen and other Gases.

THE Committee regrets to state that, owing to various circumstances, very little further progress has been made during the past year. The necessary means for securing assistance in part of the work have, however, lately been secured, and its continued progress may therefore now be looked for; and it is recommended that the Committee be reappointed. No grant is asked for, as the necessary apparatus is at the command of the Committee.

Third Report of the Committee, consisting of Professors H. M'LEOD (Chairman), ROBERTS-AUSTEN (Secretary), and REINOLD, and Mr. H. G. MADAN, appointed for the Continuation of the Bibliography of Spectroscopy.

THE collection and verification of the titles of papers on spectroscopy have been continued during the past year, but there is not yet sufficient matter for publication.

The Committee desire to be reappointed.

Fifth Report of the Committee, consisting of Professor TILDEN and Professor ARMSTRONG (Secretary), appointed for the purpose of investigating Isomeric Naphthalene Derivatives. (Drawn up by Professor ARMSTRONG.)

The isomeric dichloronaphthalenes. Since the publication of the previous report Mr. Wynne and the writer have completed their examination of the dichloronaphthalenes. As mentioned in the third report, no fewer than twelve isomerides were reputed to exist; one of these, however -strange to say, the a-modification, the oldest member of the set-has proved to be non-existent as a distinct isomeride, being a mixture of two others inseparable by the ordinary methods of crystallisation; while another has been shown to have been improperly ranked as a dichloroderivative, being a trichloronaphthalene. The remaining ten have been characterised and their constitution determined by logical and consistent arguments, which leave no doubt that they actually are the ten dichloronaphthalenes which, according to theory, can exist if the simple double hexagon formula for naphthalene be adopted.

The formula of the ten dichloronaphthalenes are given in the table below, those of the acids into which they are converted on sulphonation being given in the second column of the table, and those of the corre sponding trichloronaphthalenes in the third. In this table S is printed for SO,H; the melting points of the chloride and amide of the acid are indicated below the symbol of the acid.'

The establishment of the existence of such a series of ten isomerides formed by the introduction of but two atoms of chlorine into a hydrocarbon is in itself remarkable; it is still more remarkable when the diversity of properties which the isomerides manifest is taken into consideration; moreover the identification of ten isomerides and the recognition of their constitution afford striking testimony to the completeness of modern methods of inquiry and the truth of our theory of constitution : however much our symbols may differ from actuality, there cannot be a doubt that they afford a most accurate presentment of intramolecular relationship.

It may be added that the facts now established place it beyond question that the hydrocarbon naphthalene has a symmetrical structure such as is indicated by the conventional double hexagon formula; it remains to solve the far more difficult problem involved in the determination of its exact inner structure.

The opportunity afforded by a series of ten isomerides for the comparative study of physical properties in their relation to constitution is obviously very great, and it is intended ere long to enter on this branch of the inquiry.

The isomeric dibromonaphthalenes.-With the object of securing the data necessary for the exact comparison of the chloro- and bromo-derivatives of naphthalene, and especially the behaviour of naphthalene towards chlorine and bromine, much time has been devoted by the writer and Mr. Rossiter to the study of the dibromonaphthalenes. The results are not yet sufficiently complete to render their publication desirable.

The isomeric trichloronaphthalenes.-Theoretically fourteen isomeric trichloronaphthalenes can exist. As the determination of the constitution of a large number of naphthalene derivatives-including many of technical importance-is dependent on a knowledge of the trichloronaphthalenes, Mr. Wynne and the writer have paid much attention to their study; besides the seven already known, they have succeeded in preparing six others, and are at present endeavouring to prepare the only modification which remains to be discovered. The melting points of the thirteen known trichloronaphthalenes and their probable constitution are indicated in the following table, in which also are given the letters by which they have been distinguished.

It will be noticed that three modifications melt at about 80°, and four near to 90°; hence it is important to ascertain the distinctive properties of the several modifications, so that their identification may be rendered easy and certain. This difficult and wearisome task will, it is hoped, be completed during the coming year.

Naphthalenedisulphonic acids.-By eliminating the NH, group from beta-naphthylaminedisulphonic acid G, Mr. Wynne and the writer, since the publication of the last report, have succeeded in preparing naphthalene 13 or meta-disulphonic acid; the same acid has been independently prepared in this manner in the laboratory of the Badische Anilin und Soda Fabrik. It is noteworthy that although in a measure the analogue of benzenemetadisulphonic acid, which readily yields resorcinol on fusion with alkali, naphthalene 1: 3 disulphonic acid is converted by fusion with alkali with remarkable facility into a trihydroxynaphthalene. Five of the ten possible disulphonic acids are therefore now known. Their properties are summarised in a table in the 'Chemical Society's Proceedings,' 1890, p. 14.

Naphthylamine, naphthol and chloronaphthalene-disulphonic acids.—▲ large number of disulphonic acids of the naphthylamines and naphthols are now in technical use,' and both on this account and in order to obtain the material for a discussion of the comparative influence of NH, and OH, the constitution of these acids has been determined by Mr. Wyune and the writer, and they have also prepared disulphonic acids by sulphonating the chloronaphthalenesulphonic acids in order to compare the influence of what may be regarded as a neutral radicle with that of the alkylic NH, and acidic OH; the results have been recorded during the past two years in nine communications to the Chemical Society, and appear in the 'Proceedings.' One interesting result of the examination of the disulphonic acids, to which attention may be called, is that apparently there is an 'invincible objection' on the part of two SO,Ħ groups to remain in either contiguous or para- or peri-positions. The expression remain in' is used advisedly, as it appears probable that initially such positions are not infrequently taken up by sulphonic groups.

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The formation of beta-derivatives. In previous reports emphasis has over and over again been laid on the fact that in the majority of cases naphthalene gives rise to alpha-derivatives, beta-derivatives being formed only when a group is present which determines the entry of the new group into the contiguous beta-position or owing to the occurrence of secondary change. Attention must now be called to certain important exceptions to this rule.

A very complete description of the various naphthalene derivatives which are used technically will be found in the art. Naphthalene by Mr. Wynne in the recentlypublished vol. ii. of Thorpe's Dictionary of Applied Chemistry (Longmans).